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 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?