Doctor Who: 10 Storylines That Will Never Be Revisited

An unfortunate side effect of Doctor Who's age and premise is that a staggering amount of characters and storylines have been dropped throughout its run.

The show has been on the air for well over fifty years and has played host to dozens and dozens of writers and directors in that time, with each of these creative minds bringing some fresh ideas and concepts to the table. Unfortunately, not everything is solid gold, and the majority of these don't become mainstays.

Plus, when you factor in the standalone nature of most episodes - as well as the fact that time travel can easily overwrite and change certain things - it's pretty much inevitable that some stories will just become lost within the show's vast history.

While some of these plot points may have been revisited in comics, novels and audio dramas, the fact that Doctor Who doesn't have a clearly-defined canon means that only the core show can be considered the true, actual version of events.

Bearing that in mind then, these storylines were never picked up again after we last saw them, and frustratingly, it's highly likely that things will stay that way for good.

The main evil force in Mummy on the Orient Express was the bandaged zombie of the title, which gave its targets 66 seconds to live before killing them without mercy. However, the episode also teased a bigger, behind-the-scenes bad guy called Gus, but this intriguing setup ultimately went nowhere.

The episode established that Gus - basically an evil supercomputer - was responsible for unleashing the mummy on the unfortunate passengers of the train. This was done so that he could analyse the creature, capture it, and use its abilities for untold nefarious deeds. But when the Doctor defeats the mummy at the end of the story, Gus blows up the train and vanishes, never to be heard from again.

This left the identity and origin of Gus a total mystery: who was behind the computer? Considering that it's been years since we last saw the character and he was hardly an immensely popular breakout villain to begin with, it doesn't look like we'll ever get an answer to that question.

We did come close, though. Gus was almost included in Oxygen, an episode that aired two seasons later, but this idea was scrapped early on.