Newly arrived in Aberystwyth, DCI Tom Mathias has barely settled into his caravan when he's called to a scene of carnage. A 64-year-old woman has been brutally attacked, but she's nowhere to be found. The investigation leads to a former children's home with a cruel history.

When an elderly man is found bludgeoned to death at a remote farmhouse, Mathias must solve a historical jigsaw whose pieces include eerie photographs, the German Wehrmacht armed forces, murky land deals, an old letter, a local organization of professional men, and a love story spanning 70 years.

In the hills above Aberystwyth, divers find a young man's body in a quarry lake. The investigation pulls Mathias into the complex web of a close-knit community that lives by its own rules. An apparent suicide complicates the case, and an ex-convict's lonely life in a caravan is uncomfortably close to Mathias's own.

The body of a young woman in a scarlet dress is discovered at the center of a marshland. Mathias becomes too emotionally involved in the case, a fact that Mared notices. An old case comes back to haunt him, and a suspect takes matters into his own hands.

An arson attack on an isolated farmhouse leaves a mother and child fighting for their lives. Drawn into a community of failing farms and long-standing feuds, DCI Tom Mathias and his partner, DI Mared Rhys, are pushed to the brink as they try to solve the disturbing case.

DCI Mathias is under pressure; his estranged wife, Meg, has turned up in Aberystwyth, and he’s under investigation by the IPCC following the death of Mari Davies. When a bus driver’s body is found shot on an isolated mountainside, the investigation provides a welcome escape for Mathias. The team have a suspect to question, but Mathias believes he is an unlikely killer.