Charlie and Nicola Buchanan are a married couple who have a dirty job. They run a professional cleaning company that specializes in cleaning up crime scenes. Working that close to crime scenes, the couple inevitably find evidence and other clues associated with the investigations -- some of which the police may have missed. Every so often, the Buchanans get carried away helping to solve the cases that are eluding the police. With Charlie possessing a lot of factual knowledge and Nicola having a keen sense of justice and human behavior, the two are often able to close the cases that the cops can't.