An accident-caused by a group of space salvagers attempting to steal the TARDIS-causes the TARDIS to malfunction, trapping Clara inside, and leaving the Doctor with the scavengers. The Doctor re-enters with the scavengers, while Clara wonders through the many corridors of the giant vessel-full of libraries, strange mini-worlds, and swimming pools.
However, eventually they get stuck in a time-loop, and are pursued by horrifying monsters, who are actually messed-up versions of themselves from a possible future.
However, the Doctor is able to fix things by making sure the inciddent never happens in the first place-by talking to himself from a few hours before via a time rift.
Next, it’s back to Victorian times where the Doctor once again finds himself with the Paternoster gang-Vastra, Jenny, and Strax. This time, they’re investigating a Utopian secret society which is in fact, using the venom from an alien leech monster to preserve people and then awaken them after an apocalypse. The Doctor himself falls victim to the poison during the investigation, but doesn’t entirely freeze up due to his alien nature.
The society is led by Miss Gillyflower, played by famed British actress (and former Bond girl) Diana Rigg. She has the alien leech as a sort of symbiote with her, and wants to use it to both trigger an apocalypse, and preserve those she deems to be worthy.
The Doctor is able to stop her plans, with the help of Clara and the gang. Meanwhile, Clara, returning to the future, has taken up a job as a babysitter, much like the Snowmen version of Clara. However, due to old photos of her surfacing from her various adventures in the past with the Doctor, her wards have found out, and now ask to be taken on a trip with the Doctor.