A call for help from a former colleague leads Maine game warden investigator Mike Bowditch and his girlfriend Stacey Stevens on a sea kayaking trip to a research station far off the coast. Stacey spent summers interning on the island, a sanctuary for endangered seabirds, and they are shocked by the atmosphere of tension they encounter when they come ashore. The biologists are being threatened and stalked by a mysterious boatman who they suspect is trespassing on the refuge late at night. And now the sanctuary's enigmatic founder, whose mind has been slowly unraveling, has gone missing. Camped on an islet for the night, Mike and Stacey waken to the sound of a gunshot. When they return to the refuge at dawn, their darkest fears are confirmed: two of the three researchers have been brutally murdered and the third has disappeared, along with the island skiff.