Composed during the 14th century in the English Midlands, Sir Gawain and the Green Knight describes the events that follow when a mysterious green-coloured knight rides into King Arthur's Camelot in deep mid-winter. The mighty knight presents a challenge to the court: he will allow himself to be struck by one blow, on the condition that he will be allowed to return the strike on the following New Year's Eve. Sir Gawain takes up the challenge, decapitating the stranger...
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.