After just barely managing to escape from the Crucible, the TARDIS has crashed down on Earth in London during the year 2020 and has completely shut down. While the Doctor tries to find a way to repair it, he, Helen and Liv are shacked up in his old house on Baker Street, which has gone through quite a few changes since the last time he was in it, having been converted into flats and occupied by a host of people who are more than a little suspicious of the Doctor's odd behaviour.
While the TARDIS Team attempts to get to know their new tenants and adjust to life in a time period unfamiliar to all of them, something else finds its way into Baker Street, sowing seeds of suspicion and paranoia. Helen meets a man with a very familiar face – and a terrible warning.
Lost Property contains examples of:
- Breather Episode: Coming off the back of the epic drama of "Ravenous" that was the culmination of a massive arc beginning with "Doom Coalition", this story has considerably lower stakes, being confined to 21st century London and mostly showing the TARDIS crew adjusting to life in one place. Even the threat of whatever entity is stoking tensions in the house isn't delved into completely.
- Brought Down to Normal: Though he is still a Time Lord, the Doctor is stuck on Earth with no TARDIS, no sonic screwdriver and no psychic paper to help him out. He is more than a little crotchety at the loss.
- Call-Back:
- The Fifth Doctor left the house at 107 Baker Street to Thomas Brewster in 2008. Typically, Brewster had it converted into flats and racked up sizable debts without ever paying them off.
- Continuity Nod:
- Being without the TARDIS has a serious effect on the Doctor's mood and memory, which had previously been explored during his time in the Divergent universe.
- The Curator admits to knowing the Doctor, but says that the Doctor has not met him yet.
- When Midge tells the Doctor that he had previously left an artifact in his safekeeping when he was tall with white hair and a velvet jacket, the Doctor thinks he knows who he's talking about. When Midge mentions the other Doctor also had a Scottish accent, however, he is less sure.
- After the Curator lets slip that he knows the Doctor very well, Helen tells him the situation reminds her very much of when she first met River Song. The Curator has to tell her in no uncertain terms that he is definitely not River.
- Liv has been to the house on Baker Street before, even living there for a time with Molly.
- Eating the Eye Candy: Tony says that Ron puts up with a lot of the Doctor's eccentricities because of his very tight jeans.
- Fish out of Temporal Water: Despite his ongoing fascination with Earth, the Doctor has never sat still for long enough to understand how everyday human life works. Liv is from too far in the future to adjust properly and Helen, the closest thing they have to a local, is from more than 50 years in Earth's history. They all find it extremely difficult to navigate in 2020.
- Gossipy Hens: The tenants of 107 Baker Street, particularly Tony and Ron. After hearing that the Doctor might possibly have let a homeless man through the door, Ron starts putting it about that he's opening up the entire house for waifs and strays.
- I Never Told You My Name: Liv is extremely suspicious of the Curator when he calls her and Helen by name. Helen assumes that he simply overheard them talking to one another.
- I Was Never Here: The Curator cautions Helen not to say anything about him to the Doctor in case it messes with the timelines, saying that if she does talk about anything he said to her, she didn't hear it from him. He takes it a step further by saying that he might not even truly exist, confusing Helen to no end.
- Kleptomaniac Hero: The Doctor "borrows" Robin's game console for his experiment, not bothering to ask and not seeing what the problem with it is.
- No Help Is Coming: While normally the Doctor would just go knock on UNIT's door and ask for his old job back or some kind of support, at the time of the story the organization is dealing with major fallout from several disastrous incidents and it has been defunded.
- No Social Skills: Being cut off from the TARDIS makes the Doctor even worse than usual. His reclusive and anti-social behaviour makes him a target of fear and suspicion among the tenants of Baker Street and he doesn't help matters by refusing to learn their names or trying to be civil. Liv says outright that unless the Doctor is saving people from an alien menace, he has no idea how to talk to them.
- Oblivious to Love: Tania drops fairly unsubtle hints to Liv that she's interested in her. Liv doesn't even seem to register that she's being flirted with.
- Sense Loss Sadness: The Doctor says that being cut off from the TARDIS is affecting his mind, making his memory fuzzy and adversely affecting his mood.
- Time Abyss: When asked for his number, the Curator interprets this as questioning either his age or which incarnation of the Doctor he is (if that really is his identity). He doesn't give a straight answer, but merely says his number is "impossibly high".
- Too Much Information: Tania overshares personal information about herself for the purposes of comedy, with mixed results.
- Vagueness Is Coming: Though he still keeps mostly to the sidelines, the Curator decides to intervene in events due to sensing a great disturbance in time that threatens established history.
