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When the body of local farmer Ifan Williams is found in a remote river in the North Wales countryside, DCI Cadi John and DS Owen Vaughan are called to investigate. When she informs the man"s widow of his death, Cadi realizes there was no love lost between husband and wife. Meanwhile, brothers Siôn and Glyn Thomas seem troubled, and Siôn worries about how to protect Glyn, who has Down syndrome.

After learning about reports of animal abuse at the Williamses" farm, Cadi and Owen head there to question Ifan"s mother, Mair. From a former farmhand named Dafydd, the detectives learn more about what kind of man Ifan was. Siôn stews over his financial debt, and Father McEwan pays a visit to Glyn. Cadi finally tells Rachel about her job interview in Liverpool, prompting an argument.

After arresting Polish migrant worker Piotr Korecki, Cadi and Owen interrogate him about the CCTV footage showing his altercation with Ifan. The following morning, Siôn"s ex-girlfriend Hannah visits him and frets over the state of the brothers and their home. Cadi and her sisters gather to say goodbye to their family home on the island, and later, Rachel devastates Cadi by breaking up with her.

Cadi tries to move forward by focusing on the one thing she knows she"s good at: work. The detectives go back to Ifan"s farm, while an increasingly agitated Siôn is fired from his job at the building site. Returning home, he takes out his anger and frustration on his brother. Father McEwan"s silence about past crimes comes back to haunt him.

When Father McEwan"s body is discovered, Rachel, in her capacity as pathologist, tells Cadi she thinks the murders are linked—but she doesn"t want to engage with Cadi beyond the professional. The detectives question Dafydd, who reveals his suspicions about Ifan"s long-ago involvement in the arson attack that killed Branwen Thomas. Cadi sends a team to the Thomas house, but the brothers have fled.

A search of the Thomas home yields a clue to the brothers" whereabouts. After tracking them down, Cadi finds Siôn in dire straits—can she prevent him from doing something desperate? With the case solved, Cadi begins to pack up her desk but realizes she can"t leave Wales behind without taking one last chance.