6. The Death of Adric
Premiere: March 8, 1982
Notably upping the stakes for the too-often comfy, convivial era of the Fifth Doctor, played by Peter Davison, "Earthshock" lived up to its title twice over. First, it reintroduced the Cybermen in one of their most ruthless outings to date, and second, one of the Doctor's companions, perpetually petulant young math genius Adric (Matthew Waterhouse), met with a heroic death onscreen, an incident that would have lingering repercussions for the Doctor and his remaining mates.