The Eighth Doctor takes Lucie to Christmas in Blackpool. On the way there, they meet a strange and scary man at a diner, and a drunk bum who thinks he's Santa, and the Zygon warlord who's still happily living as Lucie's aunt Pat.
In a fit of charity, Lucie decides to take the drunk Santa guy along to have dinner at her parents' house. The gang leaves the TARDIS behind to drive the rest of the way in Pat's car.
Things quickly go wrong when (a) Lucie realises they've arrived a year early and she's already at home with her parents, (b) the Doctor realises that Pat's body has aged even though it shouldn't have, and (c) Lucie's hit by a car, ends up in a coma in the hospital as a Jane Doe, and immediately gets her coma invaded by the creepy guy from the diner.
The guy turns out to be another Zygon. Or rather, a "Zynog", stuck body-surfing forever without a body-copyer, as punishment for betraying Zygon law. Inside the coma dream world, he tries to convince Lucie to leave her body so he can snatch it. Lucie resists remarkably well for someone in a coma.
The Doctor genuinely panics and is about to drive hours back to the diner to fetch the TARDIS, travel back in time and to the hospital, and break several time and space laws just to save Lucie. When he realises that a "Zynog" is behind it, though, he instead decides to go into a voluntary coma himself and to rely on Pat to bring him back with syringes of adrenaline for his hearts. Pat takes matters into her own hands, knocks out the Doctor with a sedative and goes in to save Lucie's mind on her own. However, by that time, Lucie's heard them talking, and she finds out that Pat is a Zygon warlord who only loved her all those years out of obligation and penance. She's devastated to hear that both Pat and the Doctor kept that secret from her all along.
Meanwhile, Drunk Santa turns out to be an average guy who lost his job, and Christmas turns out alright for him when he charms the hospital lobby personnel and gets a job offer as a porter. No heroics for him, no aliens, no big sweeping space story — just a nice Christmas with happy Christmas songs.
Pat's human body has been failing for a few years, which explains the aging, and she eventually sacrifices herself to defeat the "Zynog". The guy makes a grand attempt at tricking the Doctor while inside Pat's body, but the Doctor doesn't let himself be fooled, and rather grimly stays by the alien's side during his slow, painful death.
In the aftermath, Lucie tells the Doctor that she needs to rethink her life and travel on her own from now on. She's still horrified by the fact that he lied to her about Pat, and she can't bear to be his friend any longer. She just wants to remember him as a sweet madman with a box and a poncey coat who took her on adventures and disappeared again one day. While she and the Doctor spend their last evening together on the Blackpool beach, Lucie cries. So does Sheridan Smith.
Tropes
- Christmas Episode
- Dinner and a Show: Lucie wants to go home for Christmas to enjoy all the crying and bickering and drunkenness.
- "Cavemen vs. Astronauts" Debate: Lucie reminisces about her relatives "going at it hammer and tongs" over James Bond and the neighbours hearing and drunkenly butting in.
- Downer Ending
- Gender Bender
- Going Native
- I'm Cold... So Cold...: The Zynog, as it's dying. Justified by a cold saline injection.
- Medical Horror: Lucie can feel the needle in her arm, can vaguely hear the people by her bed, but she's utterly powerless to do anything.
- Never the Selves Shall Meet: Lucie realises they've got the wrong year on the doorstep, and yells "Leg it!" just before her past self opens the door.
- No Longer with Us: When the nurse tries to tell Santa Lucie is "gone".
- Phrase Catcher: The Doctor anticipates Lucie's last time calling him a "ponce".
- Pronoun Trouble: Pat/Hagoth, formerly known as Trevor, confuses people.
- Time-Shifted Actor: It’s been 25 or so years chronologically since Pat’s last appearance, so this applies.
- Twisted Christmas
