DI Frost pursues a paedophile suspected of abducting a 10-year-old boy from a Denton Town football match. Initially, Frost is unsure whether the lad simply ran away or is genuinely the victim of a kidnapping, but when the boy is found dead and a man is found dead following a hit and run incident, the identity of the latter creates a frightening link to the missing child. When a second child turns up dead in a deserted quarry, Frost is in a desperate race against time to stop a third child being murdered. While Frost is contending with this a note arrives from a secret admirer and Mullet tries to push Frost into a promotion he doesn't want.

Frost is invited to join fellow George Cross recipients in London. He is instructed to enlist the aid of WPC Hazel Wallace as a decoy to catch a serial rapist, but it exposes her to serious danger.

The murder of a widow soon gives Frost a chance to prove his worth again, but the investigation only reveals an intriguing web of deceit, and it isn't until a forensic psychologist joins the team that they realise a serial killer is at work.

The body of Lemmy Hoxton, a small-time burglar, is found at an abandoned farm. There is a spate of break-ins where the intruder gives the sleeping children injections, which reminds Frost of a similar series a few years earlier. A man returns home late one night to find his children dead and his wife missing. Frost's investigations make as many demands on his compassion as on his professional expertise, and he makes a serious error of judgement.

Frost investigates two domestic cases. The first is the tragically straightforward murder of a cantankerous old man by his wife. The other is a more cruelly deceptive one, in which a man is killed, and his son and one of his daughters go missing: Frost tracks them down to Blackpool, where she has gone for an abortion - but who was the father? The answer leads him and DS Barnard into a tragic confrontation with an armed and dangerous paedophile.

Hazel Wallace returns from her training, as the new Detective Sergeant, and is put to work by Supt Mullett sorting out the mess left behind by DI Frost, while he is on extended compassionate leave. Before long she is called upon, when a man is found hanged in his home, and she suspects it was not suicide. Routine investigations show that a fresh set of fingerprints at the scene belong to an unidentified man who had been found drowned a year previously. Frost is summoned back by Supt Mullett to sort things out, and he connects a painting that appears to have been stolen from the hanged man with an art robbery & murder some years before.

Frost investigates two deaths: a homeless teenage girl, found beaten up and drowned in Denton's river; and that of an environmental health officer, after a dismembered arm is washed up on the shoreline. This leads to the investigation of a local meat processing factory.

Frost's Christmas is overshadowed by a local power station worker falling to his death in a mysterious accident, shortly after he was burgled. Then a young police detective, Tim Fox, is murdered, and Frost wonders if it really is related to the large investigation he was working on to uncover a car theft gang.

With the railroad murder solved, Frost tries to come to terms with having an previously unknown daughter. Detective Reid is sent to look for contraband cigarettes, but is found nearly dead on a public toilet. Was he high, or did Frost´s lookalike have anything to do with it? Meanwhile, Frost eliminates suspect after suspect in the surgeon murder, and ends up saving several lives.

Background enquiries turn up two previous deaths, which appear related to the case. But their initial suspect, armed bank-robber Charlie Lehman, turns out to have died in prison over a year earlier. As they work to profile the killer they are hunting, Frost starts to get close to Hartley personally as well as professionally, though neither realises just how closely she is linked to the case until it is almost too late. Frost has a race against time to find where she is being held.

Three naked bodies are found buried, and laid out in the shape of a triangle. Meanwhile, there is trouble when a multi-millionaire businessman decides to relocate his corporate headquarters to Denton.

The first in the final two-part episode in the series sees Frost attempting to crack an illegal dog-fighting ring, only to discover that its manager, a wealthy Denton businessman, has links to a drug-smuggling operation. Frost also begins to form a relationship with RSPCA Inspector Christine Moorhead, and attempts to finally get over the death of his wife.

Frost considers retiring from the Police force and plans to get married, ending the series, however DS George Toolan dies of heart failure following a collision outside the church where the wedding is about to take place. It is noteworthy that an alternate ending was filmed, where Frost is killed instead of George, but David Jason chose the 'happier' ending over this one.

Frost's house is burned down, and he moves in with a colleague temporarily. A mysterious, ruthless kidnapper on a motorcycle tests Frost's skills to the limit. It proves a tough case to crack, and for the abducted woman, time is running out.

A vital witness to a gangland killing goes missing before she can give evidence in court, And frost finds himself under pressure to find her and her son before a hitman can get to them. Frost thinks he has won the lottery but he has lost his ticket!

Denton's last remaining quarry is vandalised. Frost finds a baby in his office and is delighed to discover it belongs to DS (previously WPC) Hazel Wallace. He gets Hazel to look into some burglary's that have been occuring just after removal jobs have been completed. At the quarry a second body is found, which causes them to call the police. The only witness to the murder is an autistic boy, who immediately becomes prime suspect. Frost finds out about some dodgy dealings in the past between the quarry owner and his former partner. The boy escapes through a window and the Officers on duty get a sever telling off. A woman comes in saying her 7-year-old son has been abducted by her husband. The quarry owner then turns up dead in a brook a small way from the quarry. The boy is found but he has rigged the Autistic boy is found and he has rigged Denton Quarry with explosives and threataning to blow the quarry and himself up. Frost manages to get the boy down but the explosives in the boy's bag still explode. Frost then goes and arrests the quarry owner's partner for the double murder and finds the other boy safe and sound in a removals depot. He arrests the missing boy's father for robbery.

Frost investigates a series of break-ins and brutal attacks at the homes of elderly people. He is helped by a female detective, DS Lawson, who also offers him advice on his personal life.

An 8-year-old girl is missing, and the last person to have seen her is Billy Conrad, a gentle young man with Down's syndrome, but who appears is hiding something.

A young woman is found viciously stabbed to death. Frost consults the victim's personal organiser, from which a trail leads him to a religious community.

A sub-postmistress is fatally stabbed in a small-scale robbery, and Frost wastes a lot of time questioning the leading suspects. Then, Helen Tudor, a beautiful first-year psychology student and keen swimmer at Denton University, is attacked on the campus, and suspicion initially falls on her psychology tutor, Keith Michaelson, but Frost's investigations uncover a link with the death of another beautiful young girl swimmer two years earlier, in another town.

Pole dancers, false passports and murder. A lethal combination of events draws Inspector Jack Frost and his new assistant into a tragic case of lust, greed and death

Upon investigation, Frost discovers that the apparently accidental death of a drug addict was actually murder. He also decides to confront an aspect of his own past.

Frost is held at gunpoint by a drugs dealer, a Territorial soldier is shot dead on an exercise, and a security van is robbed by a shotgun-wielding gang. Frost investigates the three incidents, and tries to find any links between them. His intrusions onto the army base stir up hostility from the commanding officer.

After a seven-month long suspension, Frost is back on the job. His first case is a floater in Denton River, with £6000 in his pockets. The man also carries with him a list with four sets of mysterious numbers, and the keys to two different cars. The local dance competion is the venue for another drama: a missing con man who recently switched dance partner, and a woman with a Hollywood name and a terrible temper - who keeps on ordering new fridges for her dance partners... But Frost is more interested in getting his teeth back in order after a particularly vicious lollipop.

Frost responds to a call for help but, when he arrives at the scene, all he finds is a disembodied leg… and a crocodile!