The episode “Warriors of the Deep” was the first from the final season of Doctor Who to feature Peter Davison as the Doctor. The show took a darker and somewhat more pessimistic turn with this episode, foreshadowing some of the direction in the most recent seasons.
This episode marked a return of two related species from the Jon Pertwee era, the Silurians and the Sea Devils. The Silurians have since featured in the post-hiatus series as well.
The Doctor and his companions find themselves in a seabase in the Earth’s not-too-distant future. The political situation in that time is said to mirror that of Tegan’s experience, and the episode’s context in the 1980s. Two major power blocks are in conflict with one another, as during the Cold War.
The return of the Silurians is a threat to all humankind, and ought to lead to an end to such interhuman petty squabbling. Of course, it doesn’t. The Silurians, having previously sought peaceful coexistence with humans and been rebuffed, now seek a “final solution” that will simply use the weapons of mass destruction humans have created and pointed at one another to accomplish the purpose for which they exist.
When humans see no problem in using a poison that will kill the Silurians and Sea Devils, the Doctor wonders why he is so fond of humans. And in the end, using the poison because no other way to save humankind seems to be available, leading to the death of all Silurians and Sea Devils in the base, the Doctor expresses the conviction nonetheless that there “should’ve been another way.” That is the final shot of the episode before the credits, a darker and more pessimistic ending than typical – but not unprecedented. Even back in the William Hartnell era, the Doctor commented on what a waste the loss of life had been at the end of the episode “The Daleks’ Master Plan.”