When Detective Alana Mack arrives at Clonabee police station, in a small Irish seaside town on the outskirts of Dublin, she doesn't expect to find a distressed two-year-old girl sobbing on the floor. Abandoned in a local supermarket, the child tells them her name is Casey. All Alana and her team have to go on is a crumpled note begging for someone to look after the little girl. This mother doesn't want to be found.

Meet Janine Lewis. A single mom of three and Manchester’s newest detective chief inspector. Her cheating husband walked out the day she got promoted. Now she’s six months pregnant with his baby and in charge of her first murder case. The body of a deputy head teacher is found on a lonely allotment. Gutted—his stomach sliced open—and left for dead. The only witnesses are a dying elderly man and a seven-year-old girl. And now the prime suspect has disappeared.

DI Jan Talantire is called to a cottage in Ilfracombe, where the female occupant is found dead, impaled with a crucifix. The woman, who had been renting the house for a few months, is well known locally, but the documents at the house indicate her real name is Ruth Lyle. The name means nothing to the young PC who found her, DI Talantire knows this cannot be the body of Ruth Lyle.

When a woman's body is discovered in a cathedral and hours later a young man is found hanging from a tree outside his home, Detective Lottie Parker is called in to lead the investigation. Both bodies have the same distinctive tattoo clumsily inscribed on their legs. It's clear the pair are connected, but how? The trail leads Lottie to St Angela's, a former children's home, with a dark connection to her own family history. Suddenly the case just got personal.

When a landslip on Pembrokeshire’s stunning coastal path reveals the harrowing remains of two bodies, ex-DCI Evan Warlow’s quiet retirement is shattered.