Jonathan Anselme (Harry Treadaway), a young English academic, teams up with Max Bohm (Danny Keogh), an amateur ornithologist, to follow storks on their migration from Switzerland to Africa. Max wants to find out why some birds never return from this journey. However, after Max is found dead in mysterious circumstances, Jonathan decides to make the trip alone, never suspecting that he will find himself caught up in an international web of intrigue. While Swiss Detective Hervé Dumaz (Clemens Schick) investigates Max Bohm's murky past, Jonathan is forced to confront his own troubled history. He uncovers a trail of grisly murders travelling through Bulgaria, Turkey, the Middle East, and the Congo, along the pathway of the migrating storks and their deadly secret.