Masters is on scene when a pub landlord discovers the body of a prostitute, Kelly Porterfield. Her ex-boyfriend Andy Donnelly is a suspect for Kelly's fatal overdose. His girlfriend, Jen Kilshaw, is obviously underage, so Masters focuses on getting her away from Andy. Masters promises Kelly's mum that she will bring down who is responsible. Walker, Heaton and Masters look at two overdoses, including Kelly's, and a chain of locations where the girls came from and ended up, and fear that a sex trade operation is spreading across the UK, and Andy appears to not be the main suspect in Kelly's murder or the smuggling operation.