Sgt. Merton, freshly demoted from CID, arrives at the police station to take on the new roll as Sergeant. When Ventress brings a disqualified driver in, Alf is threatned if he takes the further, the driver will reveal his past. Oscar presuades Alf to come clean, and Merton is understanding. The driver is later arrested on a drugs case. David attempts to get fit at a gymn, but things don't go too smoothly.