Nobody could ever describe "The Edge of Destruction" as a normal story. There is not a sign of a monster, no villain as such (if one discounts the Doctor), and, uniquely, it is the psychological effect of events upon the characters which is given pride of place over that of the characters themselves. For a story with modest aims: to firmly establish the concept of the TARDIS and explain some of the more mundane realities of the travellers' environment:where they sleep, how they eat, etc, David Whitaker manages to craft a tale rich in suspense and drama. The genuinely eery incidental score helps in this, establishing right from the first caption slide that this is not a typical tale, and the inspired theatrical direction of episode one creates the subliminal impression of a watcher, making the paranoid fears of the crew very, very real. The cast obviously relish having something more interesting to do than scream or look heroic, and the ultimate solution is dazzling in its simplicity. The only quibble I have with this story is that, in keeping with its status as a last minute filler, certain of the cast, specifically William Hartnell, seem not as sure of their lines as might be desired. None the less, given the nature of the story, the air of uncertainty which pervades merely adds to the atmosphere. This is one not to miss.