Philippe Sands investigates the mysterious disappearance of senior Nazi Otto Wachter, who was indicted for mass murder. The Ratline is a story of a curious death, political intrigue, spies, Nazi hunters, shadowy forces in the Vatican and a son grappling with the sins of his father.

Philippe begins by travelling to a castle outside Vienna to meet an old man who believes his father was murdered, while a voice from the past offers up clues to how it might have happened.

Producer: Gemma Newby