"Unswervingly gripping and scary, and at the same time beautifully tender and humane."--Nicci French, author of Has Anyone Seen Charlotte Salter?

When the body of a man is found crucified at the top of a hill in the British Midlands, AIDE Lock--the world's first AI detective--and Detective Kat Frank are thrust into the spotlight as they are given their first live case. When a second body is found, the police issue an extraordinary warning to local males aged between thirty and forty years old:

- Avoid drinking in pubs.
- If you insist on going to a pub, do not leave alone.
- And definitely do not leave a pub with a stranger.

With the national media and local men in an uproar, Kat and Lock have to combine their instincts and algorithms to catch the killer before they can strike again.