Nevada Barr's second in the Anna Pigeon series has a setting diametrically opposed to the hot, dry Texas setting of the first in the series. She is transferred to Lake Superior's cold, foggy environment, where she learns to operate the inter island boats; since there is no other way for a ranger to patrol the various islands in the park and rescue foolish tourists who really don't know how dangerous Lake Superior can be. She is also learning to dive. The main interest in this story is the Kamloops, a wreck deep in Lake Superior, which has been preserved complete with five of its crew members aboard. It is one of the attractions of the park for divers; but it requires experienced divers, who can go down and come back up slowly so as not to get the bends. When a pair of tourist divers tell Anna about the six crew members they saw aboard the Kamloops, she instigates an investigation, which finds Denny Castle, an expert diver, among the corpses. He had just been married, was having an affair with one of the park rangers wives, and had made a will leaving his boat and equipment to Hawk and Holly, a brother and sister who operated a diving concession with Denny. This makes for a wealth of suspects. Anna's discussions with her psychiatrist sister help Anna's thought processes and provide clues, as Anna again finds herself in danger while solving the mystery. As a matter of curiosity, I Googled the Kamloops. It is a ghoulish attraction in Lake Superior, well described by Barr. This mystery kept the reader entranced throughout. It is not for the faint of heart.