At five to midnight in Euston station, James Chiltern sends one text to all 158 people in his contacts. A message saying goodbye.

Five minutes later, with two pork pies and a packet of chocolate digestives in his pocket, he disappears.

Across the world, 158 phones light up. Phones belonging to James’s friends, his family, people he’s lost touch with. All of them now wondering, where has James gone? What happened to him? And more importantly, can they find him before it’s too late?