Sergeant-Detective Emile Cinq-Mars is summoned to Quebec to investigate a murder in this locked-room mystery with a twist: the victim is a criminal, and the suspects are already locked up . . .

Quebec, 1994. Fraud artist Abigail, the newest arrival at the Joliette Institution for Women, is struggling to adjust to the prison's communal quarters. Her fellow inmates only give out the bare bones of their crimes, and it's quite the roll call. Doi took a hatchet to her own daughter. Malka poisoned her husband. And that's just for starters. Abigail keeps her head down, does her best to make friends with the band of killers, tries to survive.

But on an ordinary, quiet day, the extraordinary happens: a prisoner is found face-down in a toilet stall, a strangulation wire around her neck. Trouble, Abigail realises, is ahead.

Sergeant-Detective Emile Cinq-Mars is summoned from Montreal to investigate. He put Abigail away - and now she's the prime suspect. But other, darker, forces are interested in Abigail, and Emile interferes at his own peril. For as he'll soon discover, in Lady Jail, nothing is as it seems . . .