A CID raid nets a gun which DS Beech believes could have been used in a recent shooting. New PC Cass Rickman is entrusted with the task of taking the gun to the lab for forensic testing, but when she stops the car to render assistance to a mugging victim, a young man reaches in and steals it. Borough Commander Mannion arrives to take charge of the investigation - Operation Loose Cannon. DS Beech's contacts come up with someone wanting to sell a gun, and he, Brownlow and Rickman organise their own operation to retrieve it, with Rickman posing undercover as the buyer. Rickman meets Leroy Jones, and Endean and Andrews, the original owners of the gun who want it back, but the operation is blown when Mannion's team almost raid the pub where the meeting is taking place. Rickman arranges to meet Jones later, and buys the gun back, but is attacked by Endean and Andrews. She fires the gun in the air, which scares them off, and alerts Brownlow, Mannion and Beech to her position. Leroy Jones is a