Nadir and Walker investigate a fire at the warehouse of a clothing supplier, but Walker suspects that all isn't as it seems when she and Harman discover a stash of fake stock in the apartment of one of the business directors. With CCTV proving that he was at the warehouse on the night of the fire, the pair are convinced they have found their man - until some crucial evidence takes the case in a completely different direction. Meanwhile, Valentine continues to support witness Kathy Clarke after she is attacked by one of the relatives of the defendant she is testifying against in the arson case, and when Kristen Shaw is assaulted, Nadir takes matters into his own hands and confronts her attacker.