Doctor Who: 10 Times The Doctor Lost
3. When Adric Was Killed In A Freighter Crash
Companions rarely die on Doctor Who, no matter which era you're talking about. Amy Pond was sent back in time and lived a happy life with Rory, Donna Noble was last seen getting married, and Harry Sullivan simply chose to leave the TARDIS behind. Death really isn't that common, and this makes the episodes where it does happen some of the most notable down-points in the Doctor's long history.
The sad end of maths genius Adric is one of the most infamous examples of this. In the Fifth Doctor story Earthshock, the Doctor and his companions come face-to-face with the Cybermen, who, as expected, are trying to destroy the Earth. Their plan is to crash an enormous freighter into the planet, and so Adric, stuck onboard said freighter, does his best to interfere.
The Cybermen have locked the ship on a collision-course with Earth, leaving it up to Adric to break the lock and save humanity. On his first attempt, he manages to send the ship back in time roughly 65 million years, around the same time the dinosaurs were wiped out. He tries again and again but is unable to prevent the inevitable, and the freighter - with Adric inside - crashes onto prehistoric Earth, destroying the dinosaurs and obliterating Adric in the process.
When this happens, the Doctor just stands there in disbelief, unable to comprehend that one of his closest friends just died before his eyes. It's one of the most tragic moments in Doctor Who history, and for the Doctor - who considers himself the ultimate protector - one of the most shattering experiences he's ever had.