First of two, at the risk of spoiling an unnecessary surprise.
Forty years ago today, as of this writing, Adric bit the big one in the last episode of Earthshock. Although that shouldn’t qualify as a spoiler, it is in an odd sense that we’ll circle back to in a moment. It really was a big moment in the classic series, the first time a companion had died in the course of a story since Katarina in The Daleks Master Plan.
The thing about Katarina though is that she is considered a companion by Conventional Wisdom (capital letters intended). By that thinking then Adam should have been a companion in Series 1 or Mickey in Series 2, and they were not similarly exalted. But as big a moment as it was when Adric went boom, his was not even the first companion death of that season, and that companion had been travelling since late sixties. In terms of story the Sonic Screwdriver is quite rightly often seen as a jet-out-of-jail free card, first appearing on this very day back in 1968 in Fury from the Deep and persisting all the way through to its own end … in 1982 with episode 3 of The Visitation.
It wouldn’t be seen again until the 1996 TVM when both the McCoy and McGann had reason to brandish it. Peter Davison remarked that he felt he had just lost an old friend. Another, possibly less beloved, would soon follow.