When Evie Winstanley's father, a collector of occult books, dies in suspicious circumstances, she decides to investigate . . . even though private detection is no profession for a woman of standing in Edwardian Britain.

When Evie stumbles across a mention of the mysterious 'circle of shadows', she begins to suspect occult involvement. Her pursuit of the truth leads her via a séance in a house on the Yorkshire moors, to legends of an ancient monster, and a sinister cult hidden amongst the elite of an Oxford University college.

But some things are better left undisturbed, and when the body of a young woman marked with occult symbols is discovered floating in a river in Oxford, Evie realises that this is far bigger than one death . . . and that her own life, and the lives of those she loves, might very well be in danger.