Jack Frost is initially reluctant to respond to a telephone request for help from Kevin Flanagan, a man who had gloated over Frost and Supt Mullet when the prosecution case against him failed. However, when Frost hears the cries of a tortured man in the background, he realises the seriousness of the situation and heads to Flanagan's farm with DC Robert Presley.
Arriving at the farm, Frost and Presley encounter a crocodile: Flanagan is nowhere to be seen. Frost searches the farmhouse and finds an old cellar containing an array of exotic animals while, on the grounds of the farm, Presley finds an amputated leg. Frost presumes that it is Flanagan's, and that the rest of the body is in the lake… or in the crocodile.
Elsewhere, the Harris family return from a camping holiday to find a naked male body in their bedroom. Geraald Harris assumes that the man was the lover of his wife, Christine, and that she is somehow involved in his death.
Flanagan, alive and well, turns up at the police station next day. He is taken into custody as the witness to the murder of his friend, an oriental man whose remains are found in the lake. He is later released on surveillance, in the hope that he will lead police to Kenneth Shaw, the leader of a local smuggling ring.
Frost, Presley and WPC Harmison are called to the Harris's house. The body is identified as belonging to Patrick Bartley, an art teacher. Frost and DS Toolan search Bartley's studios and discover revealing photographs of Carol Haymarsh, a music teacher. Haymarsh is questioned, but seems unabashed at the nature of the photographs.
The Harris's son, Adam, admits to having given his house key to a friend, and it becomes clear that Bartley wasn't Carol's lover…