Maria Jackson wakes up one morning to find that no one remembers Sarah Jane Smith and that a strange woman named Andrea Yates is living in 13 Bannerman Road. To make matters worse, a meteor that only Sarah Jane knew about was headed toward Earth. Maria realizes that the timeline has been changed somehow and that she remembers the original timeline because Sarah Jane gave her a puzzle box they received from an alien soothsayer. Sarah Jane had been told to give the box to the one she trusted most.
Researching old newspapers in the library, Maria learns that Sarah Jane and Andrea were friends when they were teenagers. The two had snuck onto a closed pier during a school trip. According to the article, Sarah Jane fell to her death. However, Maria sees the words in the article flash between Sarah Jane Smith and Andrea Yates. Maria realizes that Andrea was meant to have died on that pier. Angry, Maria confronts Andrea and vows to bring Sarah Jane back.
This reawakens Andrea's memories of the accident. As she'd hung from the pier all those years ago, the Trickster offered to save her life by putting Sarah Jane into her place. Andrea accepted the offer, sending Sarah Jane to her death. The Trickster then wiped Andrea's memories but gave her a puzzle box similar to the one Sarah Jane gave Maria.
Andrea cannot stand being reminded of what she'd done, so she asks the Trickster to wipe Maria's memories. The Trickster says he cannot because Maria is protected, but he can remove her. Andrea agrees and the Trickster sends his servant, a Graske, to capture Maria and teleport her to another dimension. Maria manages to escape and ends up in the sixties and meets Andrea and Sarah Jane right before they go to the pier. She tries to dissuade them from going to the pier but they do not listen, thinking her insane. The Graske finds and captures Maria again. She is whisked off to a white, empty world where she is reunited with Sarah Jane. However, Alan was holding Maria's puzzle box and still remembers her.
Sarah Jane is summoned by the Trickster, who explains his motivation for saving Andrea. By removing Sarah Jane from the timeline, he will allowed the Earth to be destroyed by a meteor. He also removed several of her enemies, such as the Bane, who would have conquered or destroyed the world for a reason. The meteor's destruction of Earth would be a chance occurrence, producing the chaos that he feeds on.
Earth becomes aware of the approaching meteor and news reports are being issued. Alan realizes that Maria was telling the truth about Sarah Jane and confronts Andrea. The Trickster sends his servant, a Graske, to capture him but Alan manages to knock it down and capture him. The Graske shows Alan the device he used to capture Maria and uses it to bring her back before teleporting away. Maria then opens the puzzle box, trying to bring back Sarah Jane. Alan and Maria run to the attic to see if Sarah Jane had returned. Sarah Jane can only appear in a mirror and cannot return to the real world unless Andrea cancels her agreement with the Trickster. Andrea is frightened and angered at the suggestion that she was meant to die as a teenager. Sarah Jane tells Andrea how her death inspired her to protect life. Andrea finally agrees to break her deal with the Trickster. She is sent back to the pier where she falls to her death. Her last words to Sarah Jane are "Remember me."
Sarah Jane and Luke are restored to the timeline. With Mr. Smith, they manage to deflect the meteor from Earth. Alan puts a damper on their celebrations by demanding an explanation of everything he had just seen.
- Big Bad: This episode marks the first appearance of the Trickster.
- Broken Masquerade: For Alan.
- Chain-Link Fence
- Chekhov's Skill: Alan's skateboarding past, which was mentioned at the beginning of the story and came in very handy in the climax. This trope's even been nicknamed "Chekhov's Skateboard" on Outpost Gallifrey.
- The Chessmaster: Trickster
- Continuity Nod: The Church of the Tin Vagabond was previously mentioned in the Doctor Who episode "The Satan Pit".
- Cryptic Background Reference: When listing the aliens she fought off, Sarah Jane mentions the unseen Patriarchs of the Tin Vagabond.
- A Day in the Limelight: For the Jackson family, as they attempt to restore the proper timeline.
- Death of a Child: Thirteen-year-old Andrea Yates.
- Eyeless Face: The Trickster.
- Foreshadowing: The Trickster shows an interest in erasing the Doctor from history. In Doctor Who S30 E11 "Turn Left", one of the Tricksters brigades does exactly that by enforcing a similar situation to this episode on Donna Noble.
- Heroic Sacrifice: Andrea withdrawing her agreement with the Trickster.
- In Spite of a Nail: Despite Sarah Jane being removed from the timeline, the Earth hasn't been taken over by the Bane or destroyed by vengeful Slitheen. Explained by the Trickster having prevented those as well because it wanted Earth destroyed by a random act of nature, not by a purposeful act.
- Only Known by Their Nickname: "The Trickster" is a name Alan gives to the being. The Trickster never uses the name to refer to himself.
- Out of Focus: Serial-specific: Clyde gets about three minutes of screentime in part one, and is a background character in part 2. In addition, due to being Ret Gone, Sarah Jane is only seen sparsely throughout the serial, Luke only appears at the beginning and end of the story, and Mr Smith only appears at the end of episode 2.
- Reality Warper: The Trickster, of a very limited sort; he can change or undo deaths, but only with the dying person's consent.
- Shout-Out: The title is referencing the movie What Ever Happened to Baby Jane?
- Suspiciously Apropos Music: "Always Something There to Remind Me" randomly comes up on the stereo at a particularly appropriate juncture (and it's doubly appropriate, because the event she's trying to forget about happened in the year the song hit #1).
- Timeshifted Actor: Jessica Ashworth plays the teenage Sarah Jane.