Both Barrels: Following a fatal shooting at a remote petrol station, local man Llew Morris is identified as the chief suspect. DCI Mathias and DI Rhys make a gruesome discovery at the house where Llew grew up, and then news arrives that Llew's young son has disappeared from his school. Desperate to find the missing boy and his rampaging father, DCI Mathias breaks protocol and sets off into the mountains alone.