The Assistant Commissioner has declared Sun Hill Police Station an alcohol-free zone - terrible news for Ch. Supt. Brownlow and Ch. Insp. Conway who hope to enjoy a ""liquid lunch"" when they take the A.C. to a posh French restaurant. It's even worse news for the detectives in C.I.D., who have decided they are not going to give up their Christmas party without a fight. D.C. Skase shows D.C. Croft how a police officer can get ""donations"" for the party from the local publicans, but as they return, Hicks, Brownlow and Conway arrive back from their lunch for a tour of the station. They are forced to pretend Skase is a prisoner, and an unhappy Rod is locked in the cells for several hours. An elderly man is arrested after a road rage incident in a supermarket carpark, but the police manage to reunite him with his estranged family for Christmas.
The results of the sergeants exams are in, and W.P.C. June Ackland has passed - but P.C. Gary McCann hasn't. As the relief organise a big night out in celebration of Ackland's promotion, McCann volunteers for night shift duty with P.C. Reg Hollis. Ch. Supt. Brownlow offers to pull some strings at Area to allow Ackland to stay as Sun Hill rather than transferring. Ackland politely invites Brownlow to the pub, and is horrified when he accepts. When Brownlow finally heads home, Dave Quinnan calls several minicabs to go out for a late night curry, but June and Polly are seperated when their cab driver makes off with their bags and warrant cards after being pulled over by a Stafford Row probationer, P.C. Oliver Oxley. Oxley is about to arrest them until the Stafford Row CAD officer vouches for June. June helps Oliver overcome bullying at his station, while they search for her missing bag. With the help of McCann, Hollis, and some Stafford Row officers, the cab driver is found and arrested.
While speaking to Ackland and Loxton about the problem of local dog mess, a woman is shot dead by a sniper. Meadows and his CID team are tasked to investigate, and suspect that the woman was not the intended target, and it is strongly possible the sniper was after Loxton, who is set to testify in court against an attempted murderer that afternoon. However, when Ackland's house is set alight that night, CID come to the conclusion that she is the intended target. Writing up a list of possible suspects, Ackland gets sucked into a deadly cat-and-mouse game to try to draw the killer out - resulting in the death of one of Sun Hill's best officers. 📌 Feature length rebroadcast of the episodes "Fire", "All Tucked Up" and "Bait" from Series 11.
PCs Quinnan and Stamp are first on the scene of a major chemical spill when a tanker truck hits some scaffolding near the Sun Hill tube station. Insp. Monroe arrives to supervise the evacuation of the area, as the fire department try to work out what chemical has been spilt, although a lack of documentation on the truck makes this difficult. The driver dies in hospital, but when his wife in informed by Uniform, she doesn't seem very upset. Further investigation reveals she is behind a scheme to provide unlicenced or disqualified drivers to the trucking company.
P.C. Mike Jarvis is on the last few days of the Advanced Driving Course at Hendon. He gets on well with fellow team-member W.P.C. Sommer, but both of them cannot stand the third officer in their group, P.C. Penrose, the smug, over-bearing son of a ""Black-Rat"" (traffic officer) who sees himself as the best driver on the course, let alone in the Met. The trio attends a quiz night the night before their ""final drive"", the all-important test of their advanced driving skills, and Jarvis stops Penrose from drinking too much before the test. Battling station rumours that he is being re-assessed, P.C. Tony Stamp arrives at Hendon to check on Jarvis's progress - and is pleased when Jarvis passes his final drive easily - just a few points short however of becoming a Class 1 (Area Car) driver. A hung-over and ungrateful Penrose also misses out on his Class 1 rating, but W.P.C. Sommer makes it.
Ch. Supt. Brownlow organises a tea dance for the Met Police Pensioners & Widows society. PCs Jarvis and Quinnan spend the afternoon dancing with admiring elderly ladies, WPC Polly Page is harrassed by a wheelchair-bound admirer, and PC Reg Hollis does a magic show. Brownlow is dreading the arrival of Geoffrey Allerton, an ex-copper who goes out of his way to complain about everything. When the minivan misses Allerton, Brownlow asks PC Tony Stamp to pick him up on the way to the bakery to pick up some cakes. When Stamp steps out of the bakery, he is horrified to find Brownlow's car has been stolen whilst Allerton was buying some tobacco. Packing Allerton and the cakes onto a bus, a desperate Stamp tries to retrieve Brownlow's car after it is impounded. When Allerton arrives at the dance at last, he causes a fuss when he recognises an armed blagger from a fifteen year old case at the wedding next door.
A man comes in to Sun Hill and confesses to murdering a woman who disappeared five years ago. D.C.I. Meadows, who headed the original investigation, and D.C. Carver talk to him and, when they are convinced he is lying, throw him out. The man soon returns, and this time he tells Carver something that wasn't in the news stories making the police take his confession more seriously.
Uniform and CID are on the lookout for escaped prisoner Jim Brodie, so both Brodie's wife and his drug dealer are under observation. PC Nick Slater and WPC Cathy Marshall pursue two burglers down to the riverfront, where one of them gives Slater a severe beating. Marshall sees a person on the barges and gives chase. By the time their backup arrives, delayed by PC Reg Hollis' dodgy belly, Marshall has disappeared. When her dead body is fished out of the river, the two crooks she and Slater had been pursuing are questioned over her possible murder. Searching the barge that Marshall was last seen, CID find evidence that someone has been sleeping rough on board - and it looks like it's their escaped prisoner, Brodie. The river police intercept Brodie fleeing to Amsterdam on his friend's boat, but there is not enough evidence to charge him for Cathy Marshall's murder.