There is no doubt in Thomasina Elliott's mind that her oldest schoolfriend is a creature of habit. So when, after three years of regular correspondence, Anna's letters suddenly stop, she becomes concerned. And even more so when it transpires that her friend has disappeared without trace, in extremely odd circumstances.
The first message sent to Tom Thorne's phone was just a picture - the blurred image of a man's face, but Thorne had seen enough dead bodies to know that the man was no longer alive. But who was he? Who sent the photograph? And why? While the technical experts attempt to trace the sender, Thorne searches the bulletins for a reported death that matches the photograph. Then another picture arrives.