After receiving an anonymous call leading police to the body of an old man who has been decaying for weeks, DCI Cadi John and DS Owen Vaughn are forced to work against the clock to find out the murderer's identity. This leads them into the shadows of the slate-strewn mountains of Blaenau Ffestiniog to unlock more dark secrets.

DCI Cadi John and DS Owen Vaughan pay Karl Lewis a visit. Mia tries to draw Connor closer to her.

The community comes together to pay its respects to Geraint Ellis. Mia succeeds in drawing Connor closer to her.

DCI Cadi John has to release Karl Lewis because of a lack of evidence. Mia, Connor and Lee cause trouble for Hefin, Beca and Sion at the petrol station.

Hefin discovers Sion Wells' body at the petrol station, meaning DCI Cadi John and DS Owen Vaughan now have to deal with two separate murders.

DCI Cadi John and DS Owen Vaughan succeed in apprehending Mia, Lee and Connor, but there is only a hollow sense of victory.