Following a fatal shooting at a remote petrol station, local man Llew Morris is identified as the chief suspect. Determined to find the killer, DCI Mathias and DI Rhys visit the house where Llew grew up and make a gruesome discovery which cements Llew's guilt. Tensions escalate even further when 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. With the clock ticking, Mathias puts his life on the line. Meanwhile, independent investigator John Powell is put under pressure to close the Iwan Thomas case.