House Hunting

Bill Potts and five of her friends (Shireen, Pavel, Harry, Felicity and Paul), are seeking a house that they can share together. After not having much success, due to varying reasons, they accept an offer they receive from an elderly Landlord who they meet as they come out of an estate agent. He offers them a large mansion, at very low cost, as long as they do not enter the tower.

Bill gets The Doctor to help with her move. The Doctor, acting as Bill’s uncle, makes friends with Bill’s housemates much to her consternation. On entering the mansion The Doctor becomes suspicious of the nature of the Landlord. He is also troubled by the numerous noises the house makes, including knocking back when The Doctor knocks on the walls.

As night falls, the knocking noises grow, and Bill's friends start to disappear and the group are separated. All the exits from the house are sealed tight, preventing any of them from leaving. Bill and Shireen see Pavel half-absorbed in a wall, and the Landlord appears, striking a tuning fork which causes Pavel to disappear completely.

The Landlord

The Doctor and one of the students, Harry, discover that the house's woodwork is infested with strange cockroach-like creatures which The Doctor calls Dryads. They are responsible for drawing the others into the woodwork prior to consuming them.

Down in the basement they discover contracts from over 70 years ago. The Landlord arrives and he summons the Dryads by using a tuning fork - who then consume Harry. The Landlord admits to The Doctor that he needs the Dryads to keep his daughter Eliza alive in the tower.

Moving In

Bill and another of her friends, Shireen, manage to access the tower where they discover the Landlord's daughter Eliza who reveals herself to be completely made of wood.

The Doctor then arrives in The Tower followed by The Landlord. The Doctor reveals that the Landlord is actually Eliza's son. This triggers a long forgotten memory: As a boy, the Landlord had brought his terminally-ill mother some dormant Dryads he found, unaware of their power. When they heard a high-pitched sound from her music box, they awoke and started turning Eliza to wood to stave off her illness. Since then, the Landlord has controlled the Dryads to keep Eliza well while signing on new tenants to become the Dryads' source of nourishment.

Eliza is dismayed to find that she has been living for so long without an actual life outside the house. The Landlord attempts to send the Dryads after The Doctor and Bill, but Eliza regains control. Being able to control the Dryads, Eliza takes the Landlord into a hug, over his objections, she thanks The Doctor who, along with Bill, watches as the Dryads consume Eliza and the Landlord.

Introducing Her 'Grandfather'

Bill's friends are restored to their physical bodies and the group escape before the house collapses in on itself.

Back at the university, The Doctor offers to take over watch of the vault from Nardole. The sounds of a piano can be heard coming from inside as The Doctor enters to have dinner with whoever is inside the vault.