Penny gets pulled over after being at the pub. He thinks it is a wind-up. The officers are from Barton Street.

A girl is missing and Reg is moaning about his mealtime being curtailed. Dave finds an incriminating notebook that indicates the girl is on the game. When Dave goes to tell the family, he finds out the father already knows. Conway has an argument with Brownlow after he contacted a radio station about the missing girl. While Burnside is having lunch, he notices the girl lunching with a businessman.

Brownlow gives Conway a hard time about sick figures. Young is not feeling well and June thinks it could be stress related. Loxton goes to investigate something suspicious in a scrapyard.

CID helps uniform combat burglaries on an estate. Viv and Jim pay follow-up calls to the victims. Jim is told it is kids.

Tony and Dave rush an injured woman to hospital when the ambulance is delayed after an accident. They go to see the driver of the other car. He is a sales rep who hopes to be banned from driving. A man complains to Monroe about obstruction by Tony and Dave.

The Metropolitan Police Serious Crimes Squad sweep into Sun Hill and commandeer the station's briefing room, setting a few noses out of joint in the process. They are there to investigate the murder of a police informant, who at the time of his death was under the protection of Sun Hill CID. DI Burnside and DS Roach come to blows when Roach refuses to share the blame for withdrawing officers from the safe house, and accuses Burnside of corruption.

W.P.C. Polly Page sees W.D.S. Sally Johnson from Stafford Row plant drugs on a known dealer.

WPC Ackland and PC Loxton are on foot patrol when they are approached by a Mrs Henry with a minor complaint. A shot rings out, hitting Mrs Henry and SO19 are quickly on the scene to evacuate the officers and the wounded woman. CID, including WDS Jo Morgan who has been seconded to Sun Hill as a liaison to the Regional Crime Squad, can find no reason why the woman would be the target of a sniper. PC Loxton, who is testifying in a court case later in the day is assumed to be the target and is given SO1 protection, although subsequent raids of the suspect's property put him in the clear. That night however, as Loxton slumbers in a safe house, someone firebombs June Ackland's flat.

As it becomes clear that someone wants June Ackland dead, she is horrified to find CID digging through her painful past to discover the killer's identity. Tired of being holed up in a safe house, Ackland decides to go back on duty, as this may also draw the killer out of hiding. There is a close shave when she is seperated from Sgt Cryer on street patrol and a man pulls an imitation gun on her, although she is rescued by a covert SO1 officer. Meanwhile, a witness to the arson on Ackland's flat, Mrs Cooper, comes into the station to make a statement.

The identity of the man trying to kill June Ackland may be revealed when an ex-Army officer is overheard boasting that he was paid to ""kill a copper"". CID link him to a young man who committed suicide in prison after Ackland arrested him for dealing drugs on the Jasmine Allen. WDS Jo Morgan realises that their witness, Mrs Cooper, is behind the plan as she turns out to be the mother of the dead boy. Mrs Cooper is arrested for conspiracy to murder, and she reveals that the assassin is lying in wait for Ackland at the safe house. As Ackland and an SO1 team head off to the safe house to draw the killer out, they are ambushed by a man on a motorbike just outside the station, and Jo Morgan is killed in a hail of gunfire as she rushes to warn them.

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.