The Wedding of Sarah Jane Smith

The episode starts with Sarah Jane sneaking out of her home for "a traffic report meeting". With help from Mr Smith and K9, Luke, Rani and Clyde find her in a restaurant with a man. As they are leaving, Clyde is puzzled by the sound of the TARDIS. Sarah Jane returns home and finds out that she was spied upon, but seems happy and announces that she is seeing a man, Peter Dalton, and that she has invited him to Bannerman Road.

Sarah Jane tells Luke that she is worried about what Peter might think about her adventures. Luke tells her not to worry and that she looks happy. After Sarah Jane leaves the room, Luke also hears the sound of the TARDIS. When Peter arrives at the Smiths' house, Sarah Jane tries to hide all evidence of her extraterrestrial adventures, but a parcel arrives containing an alien creature. Rani and Clyde, who were trying to see what Peter was like, take the parcel back to Rani's house. Peter arrives as Clyde and Rani leave, but Rani's mother runs across to also look at him. In the Chandras' house, Rani and Clyde see a multi-eyed slug-like creature burst out of the parcel; detecting the alien, K9 leaves Sarah Jane's house to warn about the creature. Luke manages to explain K9 away as a prototype toy. K9 then joins Rani and Clyde in trying to catch the creature as Sarah Jane, Peter and Luke go for a meal. During the meal, Rani, Clyde and K9 manage to bring the alien slug to the attic where Mr Smith teleports it to its home planet, Polongus.

Two days later, Peter proposes to Sarah Jane, who accepts. He gives her an engagement ring, which glows red. Meanwhile, Rani and Clyde investigate Peter's home, which they find to be unoccupied. Back at the attic, Sarah Jane reveals to Luke, Rani and Clyde that she has agreed to marry Peter. Rani and Clyde tell Sarah Jane and Luke that they checked Peter's house and found it empty. The engagement ring glows again and rather than getting angry, Sarah Jane seems happy and explains that Peter has another flat in London, which she has visited many times. Mr Smith detects an anomaly when the ring glows, but Sarah Jane orders Mr Smith to deactivate.

When the wedding day arrives, Clyde still has his doubts, but Luke tells him to keep calm and not ruin the wedding, and asks him to help hide K9. When Sarah Jane enters the hotel, Rani also hears the sound of the TARDIS engines. During the ceremony, when the registrar asks if there is any reason why the couple should not be wed, the Tenth Doctor bursts through the doors, demanding the wedding be stopped. As he warns Sarah Jane to step away from Peter, the Trickster appears and kidnaps Sarah Jane. The Doctor tries to save her but she, Peter and the Trickster disappear.

As Luke, Clyde and Rani regain consciousness, the Doctor introduces himself, swiftly revealing that they and K9 are the only people in the hotel, which now exists in a white void trapped at 15:23:23; The Trickster has literally trapped them in a second, cutting them off from the rest of the world, and more importantly, cutting them off from the TARDIS, which cannot materialise properly. Using K9's sensors and the sonic screwdriver, the Doctor is able to determine that Sarah Jane is trapped in another second, deducing that The Trickster has separated the group to prevent them helping Sarah Jane.

As Sarah Jane realises what has happened, she removes her engagement ring, realising that it has been influencing her actions. Peter protests that the "Angel" (The Trickster) told him that the ring would only ensure everything worked out at the wedding, and points out that Sarah Jane accepted his proposal on her own. As Peter explains that The Trickster came to him when he had an accident at home, offering him his life and the love he never had, The Trickster states that Sarah Jane and her allies will only to be returned to the real universe when she says "I do".

While attempting to find a way out of the hotel, the Doctor confronts The Trickster, revealing that he is the personification of the Pantheon of Discord; The Trickster reciprocates with his own knowledge of the Doctor and explaining that, with Sarah Jane's marriage marking the beginning of her new life, she will forget her old life of defending Earth, creating more chaos for the Trickster to feed on. The Trickster also remarks ominously to the Doctor that "The Gate is waiting for you". As the TARDIS appears, attempting to "lock on" to its pilot, the Doctor explains that 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, with the TARDIS and the Doctor being cut off from the hotel as the TARDIS dematerialises with the Doctor still inside. However, Clyde's attempts to enter the TARDIS result in him becoming temporarily charged with artron energy, allowing him to attack The Trickster.

With The Trickster's power momentarily disrupted by Clyde's attack, the Doctor is able to materialise the TARDIS in Sarah Jane's second, telling her that there is only one way to end The Trickster's deal. As the Trickster and Clyde appear, both momentarily weakened by Clyde's attack, Sarah Jane tearfully informs 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 genuinely died in the accident, and is currently living a half-life that will only become real once he marries Sarah Jane. Though The Trickster claims that Peter is too weak to make that decision, Peter states that his love for Sarah Jane has strengthened him, ending the deal and returning the hotel to the moment before the Doctor's arrival, with Peter having vanished and nobody else but the heroes remembering anything about the presence of the Trickster or the Doctor.

As Sarah Jane later cries in the attic, she is joined by Luke, Rani and Clyde, who console her on her loss before the TARDIS materialises in the attic. After the Doctor allows the three teenagers to look around the TARDIS, he departs once more, assuring Sarah Jane that she still has an incredible life ahead of her.

• The Travist Polong from Part 1 appears to be the same alien that Sarah Jane was chasing in the hospital during the events of The Mark of the Berserker.
• Sarah Jane jokes about sending the Doctor a wedding invitation, asking if she should send it to Metebelis Three. Sarah Jane visited Metebelis Three with the Third Doctor in Planet of the Spiders.
• Sarah Jane was previously controlled by a ring in The Hand of Fear, her last adventure with the Fourth Doctor.
• Clyde states that Brigadier Lethbridge-Stewart is "back in Peru". He had just returned from a previous mission there in Enemy of the Bane, and was also described as being in South America in the 2008 Doctor Who episode "The Poison Sky". He also describes the Brigadier as being Sarah Jane's oldest friend. She first met both him and The Doctor in the first episode of the Third Doctor serial, The Time Warrior. It had been intended by the production team that Lethbridge-Stewart would indeed appear in the story and meet the Tenth Doctor, but actor Nicholas Courtney was recovering from a stroke and unable to take part.[3]
• Clyde notes his concern that Peter Dalton is simply marrying Sarah Jane for the money "her aunt left her". Aunt Lavina Smith was a recurring unseen character during Sarah Jane's tenure with the Third and Fourth Doctors, and was depicted quite elderly in 1981's "A Girl's Best Friend". Sarah Jane described herself as being "all alone" in "Invasion of the Bane" and speaks of Aunt Lavina in the past-tense in The Temptation of Sarah Jane Smith. Aunt Lavina is definitively dead in the 2002 Big Finish audio drama, Sarah Jane Smith: Comeback which states that Lavinia left her fortune to Sarah Jane, but the canonicity of that story is questionable.
• No mention is made of the absence of Sarah Jane's foster brother / foster cousin, Brendan Richards, whom Aunt Lavina reared after Sarah Jane was grown. The two first met in person in "A Girl's Best Friend". The 2002 Big Finish audio drama, Sarah Jane Smith: Comeback states that Brendan is living in San Francisco, but the canonicity of that story is questionable.
• When The Doctor calls his former companion "Sarah", Rani 'corrects' him, stating that she insists upon being addressed as "Sarah Jane". The Doctor responds that she never minded when he called her "Sarah", as the Fourth Doctor routinely addressed her as simply "Sarah" during her tenure on Doctor Who.[4]
• The Trickster previously appeared in Whatever Happened to Sarah Jane? and The Temptation of Sarah Jane Smith; The Doctor refers to The Trickster in "Turn Left" in which the Time Beetle, one of The Trickster's Brigade, alters Donna Noble's timeline so that she never met The Doctor. The Trickster is also mentioned by Jack Harkness in the Torchwood: Miracle Day episode "Immortal Sins".
• When The Doctor and The Trickster confront each other, The Trickster states that the Doctor once held the Key to Time. The Fourth Doctor assembled the Key in The Armageddon Factor, and the Fifth Doctor held the complete key in the audio drama The Chaos Pool.
• The Trickster refers to The Doctor being like "fire and ice"; in "The Family of Blood", Timothy refers to The Doctor in the same manner. The Trickster tells The Doctor that "the Gate is waiting for [him]", foreshadowing the Immortality Gate in "The End of Time".
• Defeating The Trickster and correcting the timeline always requires someone to sacrifice his or her own life: Peter Dalton in this episode, Donna Noble in "Turn Left", Eddie and Barbara Smith in The Temptation of Sarah Jane Smith, and Andrea Yates in Whatever Happened to Sarah Jane?
• The Doctor tells Luke, "Good to meet you in the flesh", and acknowledges that Luke helped him save Earth, in reference to their video conferences in "Journey's End".
• When objecting to the children's attempts to ask The Doctor for a trip, Sarah Jane reminds Clyde and Rani about their confinement to Earth by the Judoon. In Prisoner of the Judoon, Clyde and Rani were given a mitigated sentence of confinement to Earth for interfering in the Judoon's pursuit of a Veil. The Doctor nevertheless briefly sends Clyde off-world in "Death of the Doctor".
• The Doctor uses a football rattle to calm the kids down. He previously used a football rattle in the Fourth Doctor serial The Masque of Mandragora as a distraction technique.
• In the concluding scenes, Sarah Jane and The Doctor each tell the other not to forget them: this same exchange took place in The Hand of Fear, as Sarah Jane left the TARDIS for the final time until The Five Doctors.
• Sarah Jane and The Doctor meet next in Death of the Doctor, although before that they'll silently wave goodbyes to each other in "The End of Time".
• K9 Mark IV explains how he is able to navigate the three-story Smith house when he announces "activating stair-negotiating hover mode." K9 Mark III lacked hover ability, and Sarah Jane was shown lifting him into and out of her car's hatchback in "A Girl's Best Friend". K9 Mark IV is later shown in "The Gift" to use his hover mode to exit Sarah Jane's car.
• Sarah Jane's is one of two weddings of former companions The Doctor attends in late 2009; each is also attended by another former companion (in this case, K9). The Doctor briefly visits Donna Noble's wedding to give her (through her grandfather, fellow companion Wilfred Mott) a winning lottery ticket. These, along with the wedding of companions Amy Pond and Rory Williams (also attended by "future companion" River Song) in "The Big Bang" show The Doctor at three weddings of companions in less than eight months.[5] Additionally, he saves the lives of newly-wed former companions Mickey Smith and Dr. Martha Jones, though it's not indicated in what year that occurred.