Cal McGill is an Edinburgh-based oceanographer, environmentalist and one-of-a-kind investigator. Using his knowledge of the waves – ocean currents, prevailing winds, shipping records – McGill can track where objects have come from, or where they’ve gone. It’s a unique skill that can help solve all sorts of mysteries. Such as when two severed feet wash up miles apart on two different islands off the coast of Scotland. Most strangely, forensic tests reveal that the feet belong to the same body. As Cal McGill investigates, he unravels a web of corruption, exploitation and violence, which threatens many lives across the globe.