Skyrim:Lights Out!

Quick Walkthrough
# Talk to Jaree-Ra in Solitude.
# Extinguish the beacon of the Solitude Lighthouse.
# Return to Jaree-Ra.
# Head to the Wreck of the Icerunner.
# Deal with the Blackblood Marauders.
# Clear Broken Oar Grotto.

Detailed Walkthrough
thumb|right|Jaree-Ra waiting for you at the docks
A Quiet Word
In Solitude, find an Argonian named Jaree-Ra leaning against a wall under the stairs closest to the gate. Speak to him, and he asks how you would like making some gold. He then (if you indicate interest) tasks you to put out the fire in the Solitude Lighthouse. A ship called the Icerunner is due to soon come into port, and without the lighthouse fire to guide it, it will crash on the rocks. This leaves it open to be plundered. Jaree-Ra assures you that the men aboard won't be harmed, and 'may even be grateful for the daring rescue we'll perform'. After you agree to snuff the fire, he tells you to meet him again by the Solitude docks. He also warns you to not speak with him beforehand, lest you arouse suspicion.

Professional Wrecking
Head northeast to the Lighthouse. There should be no guards in the building, although you may see Ma'zaka. Once you make it to the top, activate the fire to put it out. Then travel back to the Eastern Empire Company Warehouse and find Jaree-Ra. He will tell you that the ship never made it to port, and to go and find the wreck on the north coast (it will be marked on your map). He says his sister Deeja  is already aboard, and is waiting for your arrival.

Plunder Away!
At the wreck of the Icerunner, you have two ways to proceed. The Blackblood Marauders will not be aggressive when you arrive and you can simply visit Deeja for your "reward". Or, you can begin slaying marauders. 

# If you decide to fight the marauders, simply kill everyone in sight; there are no Imperial officers or ship's crew left alive so you won't need to worry about bounty. Make your way to Deeja, kill her, and loot the note from Jaree-Ra that will start the next part of the quest. At this point, skip to the Broken Oars, Broken Promises part of the walkthrough.
# If you decide to visit Deeja, one of the Blackblood Marauders will stop you and explain that Deeja is on board the ship, two levels down. A possible bug here means the gangway to walk onto the ship doesn't always appear (see Bugs). Around the boat are various containers, mostly food items, with some locked Novice-level chests. The things washed up on shore, as well as on the ship, are regarded as the Blackblood's haul, so taking any of these counts as stealing. 
Despite Jaree-Ra's words, the sailors aboard are all dead.  Deeja is waiting down in the ship's hold. She will tell you that she was expecting you, and that you'll get what you deserve. Speak to her, and she will explain that the plunder has already been moved, and that you need to be 'taken care of'. She will then turn hostile and attack; kill her, and then loot the body, retrieving a note from Jaree-Ra which explains that the plunder is at Broken Oar Grotto, and that Deeja should kill you once you've arrived. The rest of the Marauders will now turn hostile too; fight your way back to the top deck and make your escape.

Broken Oars, Broken Promises
Once free of the ship, head to Broken Oar Grotto. In the cave is a network of scaffolding and wreckage. There are two Marauders at the top of the scaffold to the right. You can hear their conversation if you sneak up on them:

Marauder #1: ''"You've been here for a while, right? What was it like back when we could still make runs out to the coast?" 
Marauder #2: "Well, before that cave-in sealed our ships in here we could loot any size ship we wanted." 
Marauder #1: "Where did you keep all that loot? I've been here almost a year and haven't seen any of it." 
Marauder #2: "The Captain has it locked away in that drowned ship by his quarters. He says it's "to keep it safe" but I know he's just keeping it for himself." 
Marauder #1: "If only we could get our hands on that treasure. We could get out of here and never look back." 
Marauder #2: "Maybe. For now just lay low and do your job. I have a feeling we'll be rid of the Captain soon..."''

Once at the top of the scaffold, take care of the two Marauders, then follow the path up the slope. Continue along the ledge until you see the drawbridge, and take out the Marauder guarding it. Pull the lever to release the bridge and cross to the next ledge. The battle ahead will be quite tough, so it's a good idea to save beforehand. 

You have two options to continue: 

Follow the Left Path
Heading down the left-hand walkway (which is free of Marauders) will lead you around the cave and will end on a ledge overlooking the ship where Jaree-Ra is hiding. You can pick some of the enemies off from this spot with a bow or ranged magic; if not, release the drawbridge and continue across to the ship and deal with Jaree-Ra and his gang.

Into the Cave
Going into the cave on the right will bring you into the Marauder's living area, where there are two enemies but also loot. The cave comes out at roughly the same place as the walkway, but shows a path upwards towards the cave roof. A Marauder is keeping watch near the top of this path, so take care of him before proceeding to the peak. From here you have a good vantage point over the ship, and can take out more of the Marauders with arrows before they can reach you. Be aware that the path continues down to the ship on the other side, and that Marauders can easily run up behind you if you aren't careful. Defeat the marauders and kill Jaree-Ra. After Jaree-Ra is dead, loot his body and the nearby chest for a large amount of gold and various gems. The quest completes once you kill him. Additional loot can be found in the Icerunner Chest, which is located on the top deck of the shipwreck in the water.

Notes
If you have already cleared out Broken Oar Grotto, you may find that you only need to deal with Jaree-Ra.
Look out for a Marauder in the Grotto in Jaree-Ra's lair called Captain Hargar. When he's dead, loot his body for a key. His journal indicates that he has stored his treasure in a sunken boat. By the side of the scaffolding is a longboat that's snapped in two; search on the submerged deck for a Master level chest and unlock it with the key for treasure. Other locked chests, not opened by this key, are located underwater as well.
Important: If you kill Captain Hargar during this quest, Ahtar won't give you the miscellaneous quest to kill him and consequently cannot become your follower. It is therefore advisable to speak with Ahtar before entering Broken Oar Grotto to ensure that both rewards can be obtained.
There is a coin purse at the top of the masts' intersection at the main ship, but it will take careful platforming to get. It can be shot off with an arrow or spell and retrieved where it falls. You may also approach the scaffolding at the end from the water, where steps lead up to the scaffolding.
The Smithing skill book ''Cherim's Heart is on a workbench near the forge at the top of the scaffolding.
If you sneak up to Jaree-Ra without him detecting you, he will force-initiate a dialogue sequence and say either "First you murder my sister, then you massacre my men!" or "You've betrayed me, murdered my sister and massacred my men!" Your only dialogue option is "..." Select that and Jaree-Ra will then say "To Oblivion with your loot! This ends now!"''
This also happens if you already cleared out Broken Oar Grotto ahead of time and return to find only Jaree-Ra.
If Protecting the Bloodline occurs at Broken Oar Grotto during this quest, the Vampire will be found inside fighting with the Blackblood Marauders.

Bugs
 
If any followers remain stuck inside, it may be possible to release them by traveling to Solitude and paying off a bounty (if you have no bounty, create one). Upon loading by the jail, all followers should be in your party.
 
Reloading or fast traveling to another place and then back again may fix this. You can also jump from the scaffolding to the prow of the ship.
 
 
 
 
Grabbing the note and placing it in your inventory, then reading the note may trigger the quest update.
If you simply travel to Broken Oar Grotto, find Jaree-Ra and kill him, the quest will be complete without all the objectives being completed.

Quest Stages