The writers must have had their work cut out adapting the original six episode BBC TV series into just seventy minutes of film. No wonder the story starts at such a cracking pace. As soon as the opening credits fade, hospital consultant Mark Fenton is abducted to operate on a mysterious patient in a secret location. Fenton appeared in another adaptation of a Francis Durbridge TV series, THE BROKEN HORSESHOE (see my review). Here he's played by the gaunt figure of Guy Rolfe who proves ideal in the role. Fenton finds himself increasingly deeply involved in the affair of a missing diplomat in one of those thrillers where enigmatic remarks lead to sudden death and few people are quite who they seem. There's usually a sceptical copper to catch the hero in suspicious circumstances, and here Ballard Berkeley brings some character to the slightly sardonic Inspector Austin; his dealings with Fenton include some enjoyable dry humour between the pair. There's a brief uncredited appearance by William Franklyn as a colleague of Fenton's; it sounded as if he was addressed as Doctor Gillespie! It's a cleverly plotted, taut mystery, with a Cold War background, and Guillermin just about glosses over one or two inconsistencies in the narrative, caused, no doubt, by having to jettison so much of the original material.