• falls exactly on a Doctor Who episode
• falls during the Classic era's season 13
• features the 4th Doctor (Tom Baker, 1974-81)

The planet Karn is home to Solon, a fanatical scientist who is using the remnants of spaceship crash victims to put together a new body for the still-living brain of the executed Time Lord criminal Morbius. When the Doctor and Sarah arrive on the planet, Solon decides that the Doctor’s head is just what he needs to complete his work.

Writer: Robin Bland (pseudonym for Terrance Dicks and Robert Holmes)
Director: Christopher Barry

More information at Wikipedia.