In 2018, Sally Hayden received a message on Facebook: "Hi sister Sally, we need your help." It was from an Eritrean man who had been held in a Libyan detention centre. Everyone with him had tried to reach Europe, but they were caught at sea and locked up. Now, Tripoli was crumbling in a fight between warring factions, and the refugees remained defenceless, with only one hope: contacting her. A staggering account of life along the world's deadliest migration route.