Post-war England, 1952, a spate of murders is reported in the press. Susan (Anna Maxwell Martin) thinks she may have worked out a pattern to the killings of five girls. Having worked at the secret code-breaking unit at Bletchley during the war, she finds being a housewife (a husband and two children) is not enough to keep her mind active. The police tell her there is no foundation to what amounts to conjecture. Susan calls on three of her former Bletchley colleagues, Millie, Jean and Lucy to form a peace-time operation to identify any common links between the murders with a view to tracing the person carrying them out. Quickly they believe that the recent killings follow a similar method in their execution and locality with a possible railway linkage. The police take note after one of the girls literally puts her life on the line and after listening and taking action, are content they have satisfactorily tied up the case. The Bletchley girls stretch their web and uncover past murders they are convinced have been perpetrated by the man responsible for the recent abductions, but the case is by no means closed to their eyes. They lack hard evidence, leads, clues, anything to pick out and support a common trend in the crimes. Hence they plod on. No spoilers but the action becomes tense with suspense and frightening, sinister moments. The girls carry their wartime bravery and skills into the danger zone.
This is an enjoyable three episode drama portraying convincingly dress,scenery and general atmosphere of the period, especially the steam trains. It is sometimes slow and predictable but it keeps the viewer involved with the chase right to the end. Anna Maxwell Martin is, as usual in her parts, quite outstanding and brief interludes with Simon Williams (Cavendish), who knows more than he is initially prepared to divulge, add weight to the authenticity of the storyline. I enjoyed this short series which was easy on the eye and uncomplicated to follow. What will they do next when the excitement and intellectual stimulation is over?