Skyrim:Diplomatic Immunity

Quick Walkthrough
# Talk to Delphine in Riverwood.
# Meet Malborn in Solitude and give him any equipment you want smuggled into the embassy.
# Meet Delphine at the stables, wear the party clothes and hop in the carriage for a ride to the embassy.
# At the embassy, create a diversion and slip away from the party with Malborn.
# Recover Thalmor intelligence files from the ambassador's office.
# Go down to the dungeon and recover the rest of the documents.
# Obtain the key to the trapdoor and escape.

Detailed Walkthrough
The Thalmor
thumb|Malborn inside the Winking Skeever
Travel to Riverwood. If you choose to travel with Delphine, and come close to her, she will stop and explain the complex background story about the Blades and how the Aldmeri Dominion wiped out all Blades during the Great War. While her memory of past events seems checkered at best, she at least provides some background information behind her hatred towards the Thalmor and a valid reason on why she suspects them for being responsible for the dragon attacks.

Due to a travel bug, it is best to chat with Delphine at the beginning of her trip, then stop by the Braidwood Inn and rest, giving her time to travel alone. She has no special commentary at waypoints in this direction. Delphine will appear at The Bannered Mare in Whiterun and fuss at the Dragonborn for not meeting her in Riverwood.

Once back in the Sleeping Giant Inn, she will head down to the secret basement and reveal that she has a plan. Thalmor Ambassador Elenwen often throws parties for the upper-class citizens of Skyrim. You are to meet a "man on the inside", Malborn, who will help you to the best of his abilities. He will meet you at the Winking Skeever in Solitude. In the meantime, Delphine will work on getting you a formal invitation to the party. Travel to Solitude and see Malborn.

The Wood Elf
According to Delphine, the Thalmor killed Malborn's entire family back in Valenwood, giving him plenty of good reason to help you out. You will find him inside the Winking Skeever, trying to keep a low profile. He will be quite surprised that she picked you for such a dangerous infiltration job, but will explain the situation. You are to carefully choose some equipment that he can smuggle into the embassy, preferably stealth-based, and he advises you not to try to bring anything yourself. When you're ready, hand him your preferred equipment. Don't forget to give him lockpicks if you want to access locked containers in the Embassy. After you close the menu, he will get up and leave. 

Delphine will now be waiting for you at Solitude Stables, just southwest of Solitude. Once you arrive, she will ensure that everything went smoothly with Malborn and will then hand you an official invitation along with a set of party clothes and boots to look the part. After you have changed she will take your remaining equipment and you will automatically board the carriage to the Thalmor Embassy.

High-Class Party
thumb|left|The Thalmor Embassy
thumb|right|"I am Elenwen, the Thalmor Ambassador to Skyrim."
The carriage driver will drop you off in the courtyard of the embassy and you will be greeted by the drunken ramblings of a Redguard named Razelan, apparently a high-ranking officer in the East Empire Company. As you approach the entrance, a Thalmor Soldier will ask for your invitation, so show it and go inside. Once you enter, party host Elenwen will be quick to seek you out and ask too many questions. Luckily, your friend Malborn is standing right behind her and will soon interrupt the embarrassing conversation and point Elenwen's attention elsewhere. Talk to Malborn, who will brief you; you are to create a scene so he can unlock the back door unnoticed. 

Look around the room and check out the guests. When asking around, you will quickly notice that the guests are either hateful Thalmor or high-ranked denizens of Skyrim who only participate in the party for personal benefit. With the exception of the hostess Elenwen, the drunken Razelan, the servant Brelas and the bard Illdi (or Grete if Illdi is dead ), the guests are often randomized or determined from your previous actions before even starting the quest. 

You can quickly create the distraction by talking to Erikur. Listen to his speech, then wait for him to harass the elven server. After he is finished, walk back to him and offer to talk to her in his stead. He will be very grateful. Regardless of what you say to the server, when you return to Erikur tell him, "Yes. She said she can sneak you up to her quarters right now". He will then immediately go to her and begin to accost her, drawing the attention of the guards. Quickly return to Malborn and proceed to the kitchen. There are no persuasion checks required for this and his disposition towards you does not affect the dialogue.  


 
 

In this randomly determined conversation, Elenwen will politely ask the guests if they're liking the party. Depending if they're happy or not, their answer will vary:



The Jarls aligned with the Empire may also talk about problems running their hold due to recent events. They can either be Idgrod Ravencrone, Balgruuf the Greater, Siddgeir, Igmund, or Elisif the Fair. Again, they will choose between random lines:



In yet another conversation, the party guests (except Ondolemar) will discuss current events:


 

Furthermore, a total of eight guests can provide the needed distraction- but only if you meet the requirements, or if they like you enough:
 
 
 

Brelas: No, I'm sorry, but I can't go anywhere with you.  I won't.  Please, I must get back to my duties. 
Erikur: Don't you dare walk away from me, you slut!  Do you know who I am? 
Brelas: Please, sir, leave me alone! 
Erikur: Now you're going to be sorry you crossed me.  Elenwen!  This servant girl has been throwing herself at me in a most disgusting manner. 
Elenwen: Is that so, Erikur?  And you with such delicate sensibilities.  It must have been most upsetting. 
Erikur: I demand that you have this wench removed from my presence at once! 
Elenwen: Well.  Whatever the truth of it, I'm sure a few words with Master Rulindil will have a salutary effect.  Take her downstairs. 
Brelas: No! 
Guard: Yes, Madame Ambassador. 
Brelas: Mistress Elenwen, it's not true!  I did nothing!  Sir, you must tell her!  You don't know what they'll do to me!  Please! 
Erikur: Well, I'm glad that little unpleasantness is over.
Brelas will be found in the torture room downstairs.  You can rescue her, after which she will move to the Candlehearth Hall in Windhelm.
"Helping" Erikur in this way befriends him, whether you lie to him or tell the truth, even if you rescue Brelas from her cell later.
 
|- 
|General Tullius|| Must have finished Message to Whiterun and must not have a civil war attack going on. || N/A ||
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|Idgrod Ravencrone|| Appears if Hjaalmarch is controlled by the Imperials and you are not on the quest Thane of Hjaalmarch || relationshiprank>0 (Complete Laid to Rest) ||
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Idgrod Ravencrone: An old woman can get away with almost anything. 
Idgrod: No harm is meant to you happy fool. 
Idgrod: Right here!  I see it in your face!  The snakes writhe behind your eyes!  Get away, get away from me! 
Razelan: Hmm?  Did you say snakes?  Where?  I hate them, always slithering the way they do... what?  Are they on me? 
Idgrod: Begone, serpent!  Begone from this house and trouble it no more!  Beware of the serpent in your midst!  Beware, oh people of Skyrim! 
Elenwen: Razalan.  And you promised to behave yourself this time.  Remove him.  He's disturbing the other guests. 
Razelan: I protest!  This is an insult to the dignity of my person!  This time I'm completely innocent! / This is preposterous.  Disrespect... insulting!  I am tired of being hounded from all sides! / Madame Ambassador, you know that I would never have behaved... that is to say... well I swear I'm innocent this time! 
Idgrod: Dear me.  All this trouble over me?  I think I was confused.  There's no harm in him.  Please, let him go. 
Razelan: Absolutely not!  I protest... uh, that is, yes, of course.  I still don't understand what just... oh never mind. / That is absolutely untrue!  Uh, that is, yes, of course.  What... I don't understand why everyone... never mind.
 
|- 
|Igmund|| May or may not appear. || relationshiprank>0 and persuade(50) ||
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Igmund: It's all for a good cause, old chap. 
Igmund: Ulfric Stormcloak?  The rightful High King?  That's bordering on treason, man!  Stand up.  Stand up, I say! 
Razelan: I don't understand... did you say Ulfric Stormcloak?  Fine fellow, although a bit too fond of... I mean, no, of course, I condemn him in the most... 
Igmund: You take it back then?  You retract your statement?  Well? 
Elenwen: Razalan.  And you promised to behave yourself this time.  Remove him.  He's disturbing the other guests. 
Razelan: I protest!  This is an insult to the dignity of my person!  This time I'm completely innocent! / This is preposterous.  Disrespect... insulting!  I am tired of being hounded from all sides! / Madame Ambassador, you know that I would never have behaved... that is to say... well I swear I'm innocent this time! 
Igmund: Tell your men to stand down.  I don't need any help dealing with this kind of fool.  He isn't worth the trouble.  I apologize for the disruption to such a festive occasion. 
Razelan: Absolutely not!  I protest... uh, that is, yes, of course.  I still don't understand what just... oh never mind. / That is absolutely untrue!  Uh, that is, yes, of course.  What... I don't understand why everyone... never mind.
 
|- 
|Maven Black-Briar|| Appears unless you are on the quest Dampened Spirits or she's in the Ruling Government faction. || relationshiprank>0 ||
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Maven Black-Briar: You've got a lot of nerve, suggesting something like that, to me of all people!  If this was Riften, I'd have you thrown in the dungeon! 
Razelan: What?  I didn't... hmm?  No, listen, you must have misunderstood... I don't mean to say I wouldn't be interested... what I mean is... 
Maven: You're a disgrace to the Empire.  To think that you're actually a representative of the East Empire Company.  When people talk about the decadent, tottering Empire, it's people like you they have in mind! 
Elenwen: Razalan.  And you promised to behave yourself this time.  Remove him.  He's disturbing the other guests. 
Razelan: I protest!  This is an insult to the dignity of my person!  This time I'm completely innocent! / This is preposterous.  Disrespect... insulting!  I am tired of being hounded from all sides! / Madame Ambassador, you know that I would never have behaved... that is to say... well I swear I'm innocent this time! 
Maven: Well, now.  There's no need to ruin the party on my account.  I don't think he'll be bothering me again. 
Razelan: Absolutely not!  I protest... uh, that is, yes, of course.  I still don't understand what just... oh never mind. / That is absolutely untrue!  Uh, that is, yes, of course.  What... I don't understand why everyone... never mind.
 
|- 
|Ondolemar|| May or may not appear. || relationshiprank>0 (Complete Search and Seizure) and persuade(50). Markarth must still be under Imperial rule. || 
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Ondolemar: How dare you speak of the Thalmor in such a disgusting manner! 
Razelan: What?  I didn't... hmm?  No listen, you must have misunderstood... I would never openly insult your... that is to say... 
Ondolemar: Your insults and provocations have gone far enough!  I'd kill you where you stand if I wasn't bound by my oath as an officer of the Aldmeri Dominion. 
Elenwen: Razalan.  And you promised to behave yourself this time.  Remove him.  He's disturbing the other guests. 
Razelan: I protest!  This is an insult to the dignity of my person!  This time I'm completely innocent! / This is preposterous.  Disrespect... insulting!  I am tired of being hounded from all sides! / Madame Ambassador, you know that I would never have behaved... that is to say... well I swear I'm innocent this time! 
Ondolemar: Forgive me, Ambassador.  I allowed this... fool to provoke me.  The fault is mine.  There is no need for further disruption on my account. 
Razelan: Absolutely not!  I protest... uh, that is, yes, of course.  I still don't understand what just... oh never mind. / That is absolutely untrue!  Uh, that is, yes, of course.  What... I don't understand why everyone... never mind.
 
|- 
|Orthus Endario||Complete Rise in the East. May show up if quest has not started yet.|| relationshiprank>0 (Complete Rise in the East). || 
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Orthus Endario: Watch this. 
Orthus: Hey Razelan, remember when you told me I'd never amount to anything?  Well, I don't think you should say things like that about the Ambassador! 
Razelan: What?  I didn't... hmm?  No listen, you must have misunderstood... I would never openly insult your... that is to say... 
Orthus: I know you're drunk as usual, but that's no excuse for insulting our hostess.  I don't think anyone deserves that kind of abuse!  I've known plenty of elves who were perfectly decent people. 
Elenwen: Razalan.  And you promised to behave yourself this time.  Remove him.  He's disturbing the other guests. 
Razelan: I protest!  This is an insult to the dignity of my person!  This time I'm completely innocent! / This is preposterous.  Disrespect... insulting!  I am tired of being hounded from all sides! / Madame Ambassador, you know that I would never have behaved... that is to say... well I swear I'm innocent this time! 
Orthus: I'm sorry, Ambassador.  I didn't mean to cause such a commotion.  There's no need to have him thrown out on my account. 
Razelan: Absolutely not!  I protest... uh, that is, yes, of course.  I still don't understand what just... oh never mind. / That is absolutely untrue!  Uh, that is, yes, of course.  What... I don't understand why everyone... never mind.
 
|- 
|Proventus Avenicci|| Must be below stage 80 in The Whispering Door or have completed it  and must not be on the quest Message to Whiterun. || N/A ||
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|Razelan|| Always. || Give him a drink || 
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Razelan: Attention, everyone!  Could I have your attention, please!  I have an announcement to make! 
Razelan: I propose a toast to Elenwen!  Our mistress!  I speak figuratively, of course.  Nothing could be more unlikely than that someone would actually want her in their bed. 
Elenwen: Razelan.  What are you doing? 
Razelan: Although... most of you are already in bed with her!  But again... I speak figuratively, of course! 
Razelan: Fine, fine.  Get your hands off me.  I'll be a good boy now. 
Razelan: Wouldn't want to offend our Thalmor overlords, would we? 
Razelan: Someone bring me a drink, quick!
 
|- 
|Siddgeir|| May or may not appear. || relationshiprank>0 (Become Thane of Falkreath)  and persuade(50) ||
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Siddgeir: It's all for a good cause, old chap. 
Siddgeir: Ulfric Stormcloak?  The rightful High King?  That's bordering on treason, man!  Stand up.  Stand up, I say! 
Razelan: I don't understand... did you say Ulfric Stormcloak?  Fine fellow, although a bit too fond of... I mean, no, of course, I condemn him in the most... 
Siddgeir: You take it back then?  You retract your statement?  Well? 
Elenwen: Razalan.  And you promised to behave yourself this time.  Remove him.  He's disturbing the other guests. 
Razelan: I protest!  This is an insult to the dignity of my person!  This time I'm completely innocent! / This is preposterous.  Disrespect... insulting!  I am tired of being hounded from all sides! / Madame Ambassador, you know that I would never have behaved... that is to say... well I swear I'm innocent this time! 
Siddgeir: Tell your men to stand down.  I don't need any help dealing with this kind of fool.  He isn't worth the trouble.  I apologize for the disruption to such a festive occasion. 
Razelan: Absolutely not!  I protest... uh, that is, yes, of course.  I still don't understand what just... oh never mind. / That is absolutely untrue!  Uh, that is, yes, of course.  What... I don't understand why everyone... never mind.
 
|- 
|Vittoria Vici|| May or may not appear, unless you have started the quest Bound Until Death. || Complete The Spiced Wine  and persuade(50) ||
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Vittoria Vici: Just play along. 
Vittoria: How dare you!  You disgusting pig! 
Razelan: What?  I didn't... hmm?  No, listen, you must have misunderstood... I don't mean to say I wouldn't be interested... what I mean is... 
Vittoria: The head office will hear of this, Razelan!  You're a disgrace to the East Empire Company, and to the Empire itself! 
Elenwen: Razalan.  And you promised to behave yourself this time.  Remove him.  He's disturbing the other guests. 
Razelan: I protest!  This is an insult to the dignity of my person!  This time I'm completely innocent! / This is preposterous.  Disrespect... insulting!  I am tired of being hounded from all sides! / Madame Ambassador, you know that I would never have behaved... that is to say... well I swear I'm innocent this time! 
Vittoria: Oh, Ambassador Elenwen, that won't be necessary.  It is just Razelan, after all.  I'm sure he'll behave himself for the rest of the evening, won't you dear? 
Razelan: Absolutely not!  I protest... uh, that is, yes, of course.  I still don't understand what just... oh never mind. / That is absolutely untrue!  Uh, that is, yes, of course.  What... I don't understand why everyone... never mind.
 
|}
 

Infiltration
In the kitchen, the Khajiit cook Tsavani will complain about Malborn bringing a stranger into the kitchens, at least until Malborn reminds her of her secret Moon Sugar addiction. Malborn will then lead you into a room where you can receive the items you asked him to smuggle in. As soon as you exit through the door, Malborn will lock the kitchen area behind you and you are on your own, with the objective to find dragon-related intelligence. In the first hallway, you can eavesdrop on a conversation between two Thalmor Guards, hinting that Delphine may be wrong about the Thalmor:  

Guard #1: ''"Did you see those robes march in this morning? Who're they with? More of the Emissary's treaty enforcers?" 
Guard #2: "No. They're high mages, just in from Alinor. I guess Herself is finally getting worried about all the dragon attacks." 
Guard #1: "Ah, good. I've been wondering how we were supposed to defend this place from a dragon." 
Guard #2: "If a dragon does show up, maybe we'll get lucky and it will eat the mages first. Might give us enough time to kill it." 
Guard #1: "Ha. I'd like to see those arrogant bastards taken down a notch. Always looking down their noses at us lowly footsloggers."

After a bit of mean-spirited laughter, one of the guards will say, "Well, we'd better get back to our rounds."'' and they will both return to their duties, unfortunately in the room you will have to pass through. Note that the full set of Thalmor clothes in the adjacent room was supposed to make you harder to detect, but due to a bug, the clothes don't work, as the desired effect was wrongfully set to the Hooded Thalmor Robes. You can claim a set of hooded robes from the Thalmor wizard in the upstairs area from the first room, but chances are he will detect you and call upon the two guards from downstairs. Regardless, you can choose between two  strategies; either take the stealthy approach, with or without the hooded robes (see this section), or go on a rampage and kill everybody.

The first room contains the two talkative guards, with the Thalmor wizard patrolling the second floor. Right after their conversation ends, they will both turn their back to the door and return to their positions, giving you a chance to sneak upstairs and attempt to claim the robes by killing the wizard quietly. If not, you will have to take out the two guards and the wizard, and pick one of the two available doors leading to the outside courtyard. The area is patrolled by three Thalmor soldiers with another wizard standing guard near the front door to your target destination, the Solar of Elenwen. If you wear the hooded robes, the guards will not notice you, but the wizard cannot generally be avoided and will see through your disguise. To enter the Solar, you have a few options. The most straightforward is to fight them all. You can avoid the fight by using Calm, or by using Fury on one of the guards and then running in while they're busy with each other. Stealthy characters can fire arrows to distract the guards and pull the wizard away from the door. The door wizard occasionally looks to his left, leaving open an opportunity on his right for sneaking and invisible characters to get through the door before fully detected. Once the guards are dealt with and the way to the Solar is clear, enter sneak mode and head in.

The Informant
Once you get inside Elenwen's Solar, the true face of the Thalmor will start to show, although not in the way Delphine expected. When the door closes behind you, you should hide behind the plant in the southwestern corner and eavesdrop on the conversation between the Thalmor torturer Rulindil and his informant Gissur in the neighboring room. The conversation centers on a prisoner named Etienne and an unnamed old man:

thumb|right|''"He knows where that old man is you're looking for..."
Gissur: "But, I need that money! I earned it. I have my own expenses you know..." 	
Rulindil: "Silence! Do not presume, Gissur. You are most useful, but do not presume. We have other informants who are less... offensive." 	
Gissur: "But no one else has brought you such valuable information, have they? Etienne, he's talked, hasn't he? He knows where that old man is you're looking for, he told me himself." 	
Rulindil: "You'll get the rest of your money when we confirm his story. As agreed." 	
Gissur: "So he has talked! I knew it!" 	
Rulindil: "Everyone talks, in the end. Now, I have work to do. Leave me to it, if you ever want to see the rest of your payment." 	
Gissur: "Can I... I could help you. He'd talk to me. He trusts me." 	
Rulindil: "You'd like to come downstairs with me, is that it, Gissur? Shall we loose his bonds and put you in a cell together? You can ask him anything you like, and see how he answers." 	
Gissur: "No, no. I'll... I'll wait outside." 	
Rulindil: "That would probably be best. Now get out!"

While an insulted Gissur obeys orders and leaves the building, Rulindil will head downstairs and enter the dungeon, leaving the patrolling soldier alone with you. You can either sneak past him or kill him, as your objective is the chest in the northwestern corner. Open the chest and obtain the interrogation chamber key, Thalmor dossiers on Delphine and Ulfric Stormcloak, and the revealing document Dragon Investigation: Current Status'', which proves the Thalmor are investigating the dragon attacks as well, with Rulindil in charge of interrogating a suspect in the cells.

Torture Session
Go down the stairs and enter the dungeon, where you will arrive at a balcony overlooking a bloodstained torture room and a number of cells. If he wasn't killed in the previous room, Rulindil will be seated at the desk, while a Thalmor Soldier will do the dirty work and torture Etienne Rarnis while Rulindil asks a series of questions: 

thumb|right|''"I don't know his name." thumb|right|"And where can we find this nameless old man?"
Etienne: "Stop. Please. I don't know anything else. Don't you think I'd have told you already?" 	
Soldier: "Silence. You know the rules. Do not speak unless spoken to. Master Rulindil will ask the questions." 		
Rulindil: "Let's begin again." 	
Etienne: "No... for pity's sake... I've already told you everything..." 	
Rulindil: "You know the rules." 	
Etienne: "Noooooo!!!" 	
Rulindil: "Start at the beginning, as usual. If you persist in this stubbornness I'll have..." 	
Etienne: "No, wait! I was just... catching my breath... why wouldn't I tell you again? I don't even know anything... There's an old man. He lives in Riften. He could be this Esbern you're looking for, but I don't know. He's old and seemed kind of crazy. That's all I know." 	
Rulindil: "And his name is...?" 	
Etienne: "I don't know his name. Like I've told already a hundred- Ahhhh!" 	
Rulindil: "You know the rules. Just answer the questions. And where can we find this nameless old man?" 	
Etienne: "Like I said, I don't know! I've seen him down in the Ratway. Maybe he lives down there, but I don't know for sure." 	
Rulindil: "That will be all for now. I must say I continue to be disappointed in your lack of cooperation. I hope next time you will do better." 	
Etienne: "What else do you want from me? I've already told you everything. Listen, if you let me go I can take you to Riften, show you where- Gaaaaah!!!" 	
Soldier: "Silence, prisoner!"''

thumb|right|Rulindil attacks.
With that last punch, Etienne finally loses consciousness and the Thalmor will leave him alone. Rulindil will stay behind his desk while the Thalmor Soldier will start patrolling the area. The simplest way to proceed is to kill both of them, as your objectives are in the chest right next to Rulindil, and in the soldier's possession. From your spot on the balcony, head down the stairs and attract the attention of the soldier, then kill her as quickly as possible. Rulindil may notice this, but if not, sneak up behind him and cut his throat. He is a powerful wizard with countless spells at his disposal, so get rid of him quickly, then loot his body for a wide array of items such as spell tomes, poisons, and enchanted jewelry. It is also possible to avoid combat with high Stealth or powerful Calm magic. Now is a good time to save the game, if you want an old friend to survive and get another quest later on.

Escape the Embassy
When everything is quiet, enter Etienne's cell and tell him that you are here to help. Cut him loose and ask him if he knows anything of importance; he will then tell you about Esbern and the quest will update. You can also ignore Etienne and look in the chest by the back wall to the right of his cell, which contains a book titled Thalmor Dossier: Esbern; if you read it, the quest will also update. When that happens, take a quick run up the eastern set of stairs, where you will find Malborn, now exposed for his treachery, and two Thalmor Soldiers. They will kill him on the spot if you let them, so kill both of them quickly and don't hit Malborn. After the battle, search the corpses for the trap door key (or pickpocket the key without combat) and return to Etienne who will be waiting near the trap door, or just go to the trap door. This will also be your last chance to free Brelas if you involved her in your distraction by speaking to Erikur. 

You will now have up to three followers, completely unable to fight, but unlock the trap door and enter Reeking Cave. Down there, a troll resides, so run ahead of the fugitives and kill it before they even notice it (as they will try to fight it and get killed in the process). If you had a follower when you spoke to Delphine at the stables, he or she will probably enter the cave at this point from the other side, and help to kill the troll. You can also just run through because trying to kill a big troll with your weak followers in the way is really hard without getting them killed. Lastly, locate the tunnel with a dead conjurer, the Illusion skill book Before the Ages of Man and an Unusual Gem. Find the exit and prepare to deliver some surprising news to Delphine back in Riverwood.

In the secret basement underneath the Sleeping Giant Inn, Delphine will anxiously await your return. When you tell her that the Thalmor have nothing to do with the dragon attacks, she will be quite surprised and ask for elaboration. When you tell her that they're looking for someone named Esbern, she will be shocked: ''"Esbern? He's alive? I thought the Thalmor must have got him years ago. That crazy old man... Figures the Thalmor would be on his trail, though, if they were trying to find out what's going on with the dragons."'' It turns out Esbern is a former Blade, just like Delphine, and that it makes perfect sense for the Thalmor to blame him for the dragons. When you tell her about Esbern's supposed location in Riften, she will immediately task you with tracking him down before the Thalmor do. She will then give you a secret phrase to gain Esbern's trust, the Diplomatic Immunity quest will end, and the next quest, A Cornered Rat, will begin. Remember to claim all your belongings from Delphine's chest before leaving for Riften.

Achievements
One achievement is unlocked when you complete this quest:
 

Hooded Thalmor Robes Method
If you want to use the Hooded Thalmor Robes, as intended by the developers, either acquire some from the random Justiciars found in the wilderness, or aim to kill the wizard on the first floor. After you don the robes, you will be undercover if you're an elf, can walk past the guards (at a distance) if you are human, or will be immediately exposed if you are Khajiit or Argonian: 


If you play as an Altmer, it's even possible to tell the wizard guarding the door to the Solar that 'Elenwen wants to see him' by passing a speech check, thus allowing free access to the Solar (if you cannot pass the speech check however, he'll notice that you're an intruder and everybody in the courtyard will turn hostile). Note that once you reach Elenwen's Solar, the patrolling guard, as well as Rulindil, are scripted to see through your disguise, regardless of race.

This method is possible with a reasonably high Illusion skill (over 50) as other races by using Calm spells. It does not work for any other guards during this mission, and once you are inside the Solar, the guards will attack you on sight.

Notes
 
During the party, you are not able to ready weapons, crouch, wait, or shout. After sneaking away from the party, these functions are re-enabled.
Malborn and the two guards are not present until you pass through a trigger point. It is possible, either accidentally or deliberately, to miss/avoid the trigger point. In order for you to open the trap door you must cause those guards to spawn as they both carry the same keys to the escape trap door.
Reading the Dossier on Esbern should trigger their spawn.
Any prisoners you rescued will start to run toward Solitude shortly after exiting Reeking Cave. There is a chance they will run into a hostile random encounter and be killed. If you follow them and keep them alive they will eventually end up near the Dainty Sload whereupon they vanish. They can be encountered elsewhere later. Their deaths can also be avoided by fast-traveling once you are outside Reeking Cave. 
During the time this quest is active, Alduin can be seen resurrecting Vuljotnaak at a dragon burial mound near the intersection of Whiterun Hold's southern road and the northwest-bound road that heads to Rorikstead.

Bugs
 
 
 
 
 
 
 
 
 
 
 You can fix this with the console command,  
Another way to fix this is to empty your inventory before talking to Delphine at the stable.
 
 
 

Quest Stages