It is 1351, and the Black Death has ravaged England. Whole villages have been erased, their inhabitants slain by the plague. Survivors pick up the pieces, try to put what is left of their lives back together, all the while questioning how God could have let such a thing happen.
One of the survivors, Nick Calladine, who had been a member of the guard in a little town in Derbyshire, sets off wandering across the ravaged countryside, trying to find others like him. He comes across four survivors in the guardhouse in Glossop, a village up in the moorlands. But when one of the four dies under mysterious circumstances, and suspicion falls on the others, Nick has to rely on his powers of deduction to prevent another murder -- which next time might be his. And as he is drawn deeper and deeper into the history of the three men who survived -- the simple and superstitious Adam Holden, the dark, gloomy Tom Upstone, and the happy-go-lucky but brilliant womanizer Will Fletcher -- he finds out that all three of them have secrets in their past, that when put together, add up to murder.