Mathias is under pressure. His wife Meg has turned up in Aberystwyth and he's under investigation by the IPCC following the death of Mari Davies at the end of the last episode. When a bus driver is found shot dead on an isolated mountainside, the investigation provides a welcome escape.

The murder of a local dignitary and barrister leads to the uncovering of a tragic story of love and loss fuelled by mistrust and suspicion in the depths of the Hinterland. Why were Nora and Daniel living such a secluded life? What has Mathias discovered in the garden? Will he find Daniel before Glyn Powell gets hold of him? The clock is ticking, but Mathias knows that the relationship between Branwen Powell and Daniel is key to uncovering the truth.

The murder of a local dignitary and barrister leads to the uncovering of a tragic story. Why were Nora and Daniel living such a secluded life?

The discovery of a body in a remote lake leads Mathias and the team to investigate the complicated private life of a teacher missing from a small rural school.

DCI Mathias must solve the case of the murdered Aron Bowen, but he must deal with feuding family members and runaway teenagers first. Will he discover the truth of the matter or will the person that's stalking him get in his way?

On his first day on a new job DCI Tom Mathias investigates a blood soaked bathroom and the disappearance of 64 year old Helen Jenkins. The inquiry focuses on an old Children's home above the ravine spanned by the Devil's Bridge.

At a remote farmhouse, sixty-nine year old Idris Williams is discovered bludgeoned to death, and the investigation into his murder reveals the mountain’s bloody past.

In the isolated village of Penwyllt, the body of a young man is discovered in the murky depths of a quarry lake. But who is he, and was this an accident?

The body of a young woman is found abandoned but carefully placed in the marshes. This case, in the series finale, pushes DCI Mathias to the edge, both personally and professionally.

The series one climax saw DCI Tom Mathias pushed to the edge - with a local woman's death on his conscience and blood on his hands, his future hung in the balance. His career should have been left in tatters, but Prosser has other ideas. An arson attack on an isolated farmhouse has left a mother and child fighting for their lives. Drawn into a community of failing farms, festering resentments and long standing feuds, what is it about the case that draws Mathias in, pulling him back from the brink?