Valentine returns to duty, and he is partnered and Hardy to investigate an arson attack on the home of a social worker. Valentine becomes determined to track down a witness to the incident who called for the fire brigade, only to discover that she isn't prepared to stand up in court and identify the arsonists. With one of the perpetrators appearing to have pimped out his own brother in return for blackmail money, Valentine tries to get the youth to cough up his brother to save his own skin. Meanwhile, Sim and Nadir investigate when a clinical registrar disappears after receiving a number of blackmail letters and threatening phone calls, but soon discover he may have left of his own accord.