 DI Jack Frost investigates the stabbing of a woman during a robbery at a sub-post office. He is convinced that they have the culprits in custody but is frustrated by the limits placed on his ability to gather evidence. He also looks into an attack on the very pretty Helen Tudor who was pushed down the stairs at her university. She has no idea who may have pushed her but had recently rebuffed a professor, Dr. Michaelson, who had a reputation for getting too "close" to his students. In the course of the investigation, Frost learns that a woman very similar in appearance to Helen drowned some two years previously, even though she was a very good swimmer. Clive Barnard, now a DS in Boxborough, assists Frost in locating a possible suspect, a student who knew both girls. Frost finally finds himself a flat but also gets some unexpected lodgers.