10 Chilling Doctor Who Unsolved Mysteries

Tom Baker's Fourth Doctor was on a great run of form in the 1970s and early '80s, but then he had to go and ruin it by falling off a big telescope. What a silly billy.

The 1981 serial Logopolis famously marked the end of the long, popular tenure of Baker, and it also saw the one and only appearance of the Watcher.

An unsettling figure cloaked entirely in white, the Watcher appears to various characters throughout Logopolis, and seems to know a lot more than it's letting on. This strange being then reappears at the moment of the Doctor's death, merging with him to aid his transition into his next life.

It's widely believed that the Watcher is an incarnation of the Doctor – perhaps one who appears to them when they need help regenerating. But that doesn't explain his absence at other regenerations, like when Twelve flat-out refused to change. So what was it about the Fourth Doctor that required the presence of this spectral force?

Like the Midnight entity and the Beast, it's the lack of answers that makes the Watcher such a chilling mystery.