'Help me, please help me.' It was a young woman's voice, pleading with him. He opened the door, certain this was the biggest mistake of his life, and there she was, a feral creature in dirty clothes, with hollowed cheeks and scabs on her cracked lips. Her closest friend died three years ago, her body fished out of the sea off the Argyll coast, and she believes only Cal can help her find out what happened.
This is not the only unexplained death haunting Cal McGill, a part-time PhD oceanography student with a macabre interest in floating corpses. Severed feet are washing ashore on Scotland's beaches and McGill wants to know if they're wearing trainers. The answer could make all the difference between accident and murder. Then there's the tragedy of his grandfather who was lost at sea, the mystery which sparked his childhood fascination for tracking flotsam across oceans, the mystery he's now determined to solve.