Shadowy deaths have long made Grayrton Mire a place of gruesome legend. But when a vulnerable boy is charged with the latest killing, Banyard and Mingle brave the treacherous marshes to defend him.

Confronted by suspicious locals and rumours of a terrifying beast, they stumble into a deadly conspiracy. With the clock ticking and ruthless authorities determined to protect their secrets, they will need associates Penney and Lizzy to risk their lives if they are to uncover the truth.

Can they save the boy and discover who – or what – lies behind the sinister legend?

And will they survive a final night on the mire?