William Falkland is a dead man.

A Royalist dragoon who fought against Parliament, he is currently awaiting execution at Newgate prison. Yet when he is led away from Newgate with a sack over his head, it is not the gallows to which they take him, but to Oliver Cromwell himself.

Cromwell has heard of Falkland's reputation as an investigator and now more than ever he needs a man of conscience. His New Model Army are wintering in Devon but mysterious deaths are sweeping the camp and, in return for his freedom, Falkland is despatched to uncover the truth.

With few friends and a slew of enemies, Falkland soon learns there is a dark demon at work, one who won't go down without a fight. But how can he protect the troops from such a monster and, more importantly, will he be able to protect himself?