As the old saying goes, not every story has a happy ending - and that's certainly true for several of Doctor Who's companions.
Whether they were victims of error on the Doctor's part, in the wrong place at the wrong time, or a casualty of the BBC's decision to shake up the format of the show, there have been quite a few companions in Doctor Who's history who have departed in the worst and most unsatisfying ways possible.
Some of these endings were so controversial at the time that the BBC even had to apologise for upsetting viewers. Many of the actors behind these characters were also appalled at their treatment, and in some cases, after years on the show, were deeply disappointed by the fate of the companions they portrayed.
While some of these characters were lucky enough to be called back to the show later on (and others were referenced), some were simply never mentioned again after their dark, distressing, or controversial exits from the Whoniverse, and overall, it's hard not to feel like they deserved so much better.
10. Sara Kingdom
Although she was only with First Doctor William Hartnell for his legendary 12-part serial The Daleks' Master Plan, Sara Kingdom is instrumental in the defeat of the Daleks (and their plan to destroy the universe) in this story.
Much of the serial is built around the weapon the Time Destructor, which accelerates time to an extreme degree and rapidly ages everyone and everything around it. As part of his plan to destroy the Daleks, the Doctor plans to detonate the Time Destructor, and sends his companions back to the TARDIS so they do not get caught in its field.
However, Sara follows the Doctor before he sets off the Time Destructor, and she begins to age rapidly before becoming so old she turns to dust and dies. Grim stuff.
Sadly, Sara's death scene is missing (like most of the serial), but the audio still survives. She would've been a great long-term companion, and she definitely deserved better than brutally dying in her very first appearance.