Brian Elliot, a friend of Ch. Insp. Conway, has been robbed by a prostitute and her accomplice, but does not help the investigation when he refuses to make a formal statement or testify in case his wife finds out about his indiscretion. CID launch an undercover sting, which fails, but Elliot arrives at the station with his wife to make a statement, and it is quite clear she knows the truth.
It turns out to be quite an eventful first day at Sun Hill for new probationers Nick Slater and Debbie Keane.
Sgt. Boyden and probationer PC Nick Slater are called to the house of an elderly lady who claims a couple are fornicating in her garden. A search of the surrounding area turns up the guilty parties: a wealthy local businessman and his companion, Lisa Royle. Drugs are also found in their car, so the two are taken into custody. Lisa flirts with Boyden, and gives him a phone number to call to vouch for her identity. She turns out to be DS Lisa Holm on an undercover operation, and an angry DI Raymond turns up at Sun Hill to ensure the operation is not further compromised. Slater is confused when Boyden suddenly releases the pair and demands to know why, but Boyden tells him that as a probationer, there are a lot of things he doesn't need to know.
A series of unexplained robberies are cracked when one of the victims reveals she was seduced by a handsome freelance car washer, who copied her keys and arranged to meet her later, but robbed her house while she was waiting for him. Despite Insp. Monroe's objections that she is too inexperienced, DC Skase arranges for probationary WPC Debbie Keane to go undercover as a lonely housewife to catch the thief at work. The plan goes well, but at the expense of Skase's car when he uses it to block the driveway to prevent the thief's getaway.
Conway's diving team finds a corpse in a dock. Deakin and Lines have a suspect in mind, before the body is even retrieved.
When a bomb destroys a local electrical shop CID embark on a frantic search for a second device.
Carver and Woods suspect a petty thief of a much more serious offence. But are they off the mark?
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.
Sun Hill is in shock after the death of WDS Jo Morgan, none more so than WPC Ackland who is still racked with guilt over her death, and PC Loxton who is forced to apologise to a pair of loudmouthed youths after he threatens them.
A raid on a crack house sees DC Carver arrest a young prostitute, Paula, for possession of drugs. While waiting to be processed in custody, Paula is distraught, saying her infant daughter is in danger from her pimp who will hurt or kill her if he doesn't get the crack she was bringing him. Despite DS Boulton's lack of sympathy, Carver convinces his colleagues to raid the pimp's flat and save the child.