1. Episode 1 DCI Tom Mathias is a man on the run from his past. Having just left the Met police in London, he finds himself holed up in a caravan on the outskirts of Aberystwyth, an university town on the west coast of Wales sandwiched between the Irish sea and a vast mountainous hinterland.
2. Episode 2 At a remote hinterland farmhouse the body of keen photographer Idris Williams is found following an anonymous call to the police.
3. Episode 3 High in the hills above Aberystwyth, the body of an unidentified young man is found at the bottom of a lake in a disused quarry near the village of Penwyllt
4. Episode 4 The body of a young student, Alys Thomas, is found at the exact centre of a vast expanse of marshlands by two young boys.