The Wedding of Sarah Jane Smith ( TV story ) The Wedding of Sarah Jane Smith was the third story in the third series of " The Sarah Jane Adventures " . The serial was notable for the appearance of David Tennant as the Tenth Doctor , the first time that the Doctor has appeared in any of the spin - off series , and David Tennant ' s last performance as the Doctor during his original tenure , filmed after production concluded on his final episode in " Doctor Who " . The Trickster also returned for a third time . It would turn out to be his last appearance on the series , although he would be obliquely referenced in " " . Synopsis . After Sarah Jane starts acting suspiciously , Luke , Clyde , Rani and K9 investigate . They discover she has a boyfriend , Peter Dalton , and they are going to get married . Clyde suspects Peter may be an alien . At the wedding , an old enemy returns . As the gang find themselves trapped in a time loop in Limbo , can a very special friend from the past save Sarah , her friends and the entire planet Earth from the wrath of the Trickster ? Plot . Part 1 . Sarah Jane Smith is sneaking out of her home for " a traffic report meeting " . It is the fifth time this month she has made an odd excuse to the gang for going out . This time Luke activates Mr Smith and has him track her . Sarah stops on Morris Drive , where she almost uses her sonic lipstick as a normal lipstick . Luke , Clyde and Rani find her on a date , secretly seeing her new boyfriend . with a suave - looking man . They watch through a restaurant window as Sarah Jane kisses him . As the kids leave , Clyde is puzzled by a strange sound : the distorted sound of the TARDIS engines , although he doesn ' t understand what the noise is . Sarah is upset when she learns from Mr Smith and K9 that the gang have been spying on her . She says she was about to tell them . The man ' s name is Peter Dalton . Sarah forgives them and jokes with Luke that she may have to tell Peter about her investigations of aliens . After Sarah leaves , Luke also hears the TARDIS . Peter arrives , and Clyde , Rani and Gita try to spy on him . Sarah Jane is reluctant to reveal her secrets to Peter right away . She asks Rani to take a parcel that ' s been delivered to her , but it starts moving . In the Chandras ' house , a non - evil but mischievous many - eyed creature bursts out of the parcel and rampages briefly . It attracts K9 , who runs out of the house in front of Peter , but Luke passes off K9 as a prototype toy . With K9 ' s help , Rani and Clyde catch the creature and bring it to Mr Smith , who transmats it to its home planet , Polongus . Meanwhile , Sarah , Peter and Luke go out for a meal . Luke and Peter bond quickly . Two days later , Peter proposes to Sarah in a restaurant . She accepts and the surrounding crowd applaud . However , her engagement ring begins to glow red . Clyde starts to investigate Peter and tracks down his house over the Internet . He and Rani go there , but find the place virtually deserted , with newspaper covering the windows , dim , and plastic wrap covering some of the furniture . . In the attic , Clyde tries to convince Sarah that Peter may be more than he seems . Sarah claims she knows about the empty house , that Peter now lives in a flat closer to work . Rani and Luke are convinced , but Clyde is still suspicious . He is shocked to learn Sarah is getting married to Peter in two weeks . Sarah seems to be in a trance , controlled by her glowing engagement ring . Mr Smith tries to alert Sarah to alien activity in the ring but she deactivates him , saying she doesn ' t want to deal with aliens anymore and may never have to tell Peter about her secret life . On the wedding day , Clyde tries to insult Peter subtly , saying the wedding has been arranged too fast . Luke becomes angry and suggests Clyde is projecting his attitude towards his own father onto Peter . Luke wonders why none of Peter ' s family are attending the wedding ; Peter explains he has no living relatives . Sarah arrives in a limousine , with Rani as her bridesmaid . The boys react with surprise and appreciation at her dress . Clyde reveals K9 is at the wedding , further enraging Luke . When the registrar invites anyone who wants to object to speak now , the Tenth Doctor bursts through the doors shouting , " Stop this wedding now ! " Everyone is baffled why he wants the wedding stopped , but the Doctor firmly repeats that he wants the wedding stopped . Wind begins to blow inside the room and K9 emerges from hiding , saying he has detected alien activity . The Trickster materialises in a white gown and disappears with Sarah and Peter as the Doctor calls out to her . Part 2 . As Luke , Clyde and Rani regain consciousness , the Doctor introduces himself . K9 and they are the only people in the hotel . It now exists in a white void trapped at 15 : 23 : 23 , with that one second repeating over and over again . The Trickster has literally trapped them in a second , cut off from the rest of the world and , more importantly , cut off from the TARDIS , which cannot materialise properly due to the Trickster ' s time distortion . Using K9 ' s sensors and his sonic screwdriver , the Doctor determines that Sarah is trapped in a similar situation as they , but another second . He surmises the Trickster has separated the two groups to prevent them helping Sarah . Sarah figures out what has happened . She removes her engagement ring , realising it has been influencing her actions and clouding her judgment . Peter protests that the " angel " ( the Trickster in the white gown ) told him that the ring would only ensure everything worked out at the wedding . He points out that Sarah accepted his proposal on her own . Peter explains that the Trickster came to him when he had fatally fallen down the stairs at home and offered him his life and the love he never had . The Trickster declares that Sarah and her allies will only be returned to the real universe when she says , " I do " . While searching for a way out of the hotel , the Doctor confronts the Trickster , stating he is the personification of the Pantheon of Discord , a group of aliens from a different universe thriving on chaos and trying to break into this universe . The Trickster reciprocates with his own knowledge of the Doctor . He explains that , with her marriage marking the beginning of her new life , Sarah will forget her old life of defending Earth ; he also mysteriously comments that ' the Gate ' is waiting for the Doctor . The TARDIS appears , trying to " lock on " to its pilot . The Doctor explains they can use the artron energy that powers the TARDIS to fight the Trickster , but his attempt to help Luke , Rani and Clyde into the TARDIS fails . The TARDIS and the Doctor are cut off from the hotel . However , Clyde ' s attempt to enter the TARDIS results in him becoming charged with artron energy , allowing him to attack the Trickster within the Void space . The Trickster ' s power is momentarily disrupted by Clyde ' s attack . The Doctor materialises the TARDIS in Sarah ' s second . He reminds her there is only one way to end the Trickster ' s deal , and tells Peter he knows that he ' s a good man and how sorry he is . As the Trickster and Clyde appear , both weakened by Clyde ' s attack , Sarah tearfully tells Peter that the only way to stop the Trickster is for Peter to take back the deal , even though this will mean his death . Peter really died in the accident . He is living a half - life that will become real only when he marries Sarah . Although the Trickster claims that Peter is too weak to make that decision , Peter says that his love for Sarah has strengthened him and that he was right , they are the perfect match for each other . He ends the deal , throwing his ring into the Trickster , who bursts into flames , screaming in agony . Peter and Sarah Jane reaffirm their love for each other before he disappears forever . The two seconds merge and the Doctor , Luke , Clyde , Rani and K9 run in and huddle together as time begins moving forward again . . . Everyone returns to the hotel at the moment before the Doctor ' s arrival . Peter has vanished and nobody but Luke , Clyde , Rani , K9 and Sarah remember the Trickster or the Doctor ( who has also disappeared ) . People begin to whisper where Peter has gone and a tearful Sarah announces that the wedding is off . Later , as Sarah contemplates in the attic , she activates Mr . Smith and is joined by Luke , Rani and Clyde , who console her on her loss . The kids lament that the Doctor disappeared without saying goodbye , but Sarah notes that sudden vanishing acts is something the Doctor is known for . At that moment , both Mr Smith and K9 detect a temporal flux as the TARDIS materialises in the attic . The Doctor tells Sarah that he wouldn ' t just take off without a proper goodbye , and allows the three youngsters to come inside and look around the TARDIS control room . They soon exit , however , to give Sarah and the Doctor a chance to say their good - byes . The pair recall their first parting , thirty years earlier , and each tells the other not to forget them . As he departs on his travels again , The Doctor assures Sarah Jane that she still has an incredible life ahead of her , and suggests that they may still see each other again . . . Story notes . Filming locations . " to be added "