The Spare-Part People

The Spare-Part People, also known as The Brain Drain and The Labyrinth was an unproduced script written by Jon Pertwee and Reed De Rouen for Season 8. It was submitted in the summer of 1970, but was rejected after the production team decided they wanted the Master to feature in every story that season. Pertwee tried to rework the script, but Rouen was attached to the original version and stepped down from the project altogether. Pertwee later stepped down as well.

The first version saw the Doctor investigating a series of disappearances at Cambridge University. The second version saw the Doctor and UNIT hunting down the Master. In both versions, this led the Doctor to Antarctica, where he found an alien crew that was kidnapping humans and using their organs to sustain themselves. He defeated them by exposing them to a bacteria that made them allergic to human DNA, forcing them to fix their ship and leave to find another species to prey on.

In the second version, Pertwee suggested that these aliens were the ones who called the Master to Earth, hoping that he could kill the Doctor and prevent any chance of them being discovered. There may also have been the revelation that the Master had killed the Doctor's parents in this version of the script.