When an armed man massacres several people in central London, Claudine witnesses the whole thing. To her horror, one of the victims is her brother, Jethro.

Riven by grief, Claudine retreats to the house in the Fens where she and Jethro grew up. When the police contact her, she is left reeling when they tell her Jethro orchestrated the attack.

Why would a gentle, if troubled, middle-aged man cause such bloodshed – and why would he include himself in the list of victims?

Claudine finds herself down a rabbit hole of mystery, caught up in Jethro's research on a medieval cult. If she can't solve the riddle in time, more people will die... and the darkness will claim her too.

This twisty, unrelenting thriller is perfect for fans of Ruth Ware, Emma Kavanagh, and Sharon Bolton, using themes of grief to explore how people are never as straightforward as they seem.

Reviewers on D.L. Mark:

'Mark is an extraordinary talent – one of the best in the business. I adore how he writes.' M.W. Craven
'Dark and compelling with characters you will never forget.' Elly Griffiths
'Mark is a wonderfully descriptive writer.' Peter James
'Mark’s books are always taut, intelligent page-turners.' Abir Mukherjee