English couple Richard and Robin Mariner are soon to launch the revolutionary SuperCats, their fast ferry service from Thunder Bay across the Great Lakes of Canada. But when the naked body of a young woman is discovered on the lake, the ensuing murder investigation takes precedence over their test-runs.

The dead woman's identity is a mystery -- neither the Royal Canadian Mounted Police nor the FBI can shed light on who she was. But French-Canadian Jeanne La Motte -- who, with her Mohawk blood, is no ordinary Mountie - is assigned to the case, and she quickly links this murder with an earlier one at Point Noir. With Richard and Robin's help, the investigations turn to a mysterious Russian freighter that has been spotted off the Canadian coast . . .