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.

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 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.

A ruthless kidnapper holds a supermarket chain to ransom by threatening the life of a young boy.

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.

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 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.

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.

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.

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.

A man is released on licence after serving 20 years for the murder of a 14-year-old girl. When the body of her best friend, who disappeared at the same time, is found, Frost has to investigate a 20-year-old murder.

Frost investigates an MP's son who is involved in a hit-and-run accident, and a robbery at a private casino, which occur on the same night. He gets a humorless new partner to assist him.

Frost is called upon by Supt Mullett to investigate the theft of his friend's car from their golf club by a confidence trickster, who leaves behind a trail of satisfied golfing widows, unpaid bar bills and stolen cars. It gets complicated when the car is recovered with the body of a local drugs dealer in the boot. What are the connections between the car owner, the con-man and the dead drug dealer?

While Denton´s female population has to watch out for a con man posing as Frost, Frost himself has more dire concerns: a woman found dead by the railroad. To top it off, Frost has to work with a soon-to-be wash-out with possible drug problems. Then a disliked surgeon goes missing, and turns up dead.

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.

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 man's church confession provides an insight into what appears to be a straightforward murder. But before Frost can make an arrest, he is suspended over the outcome of a related case 10 years earlier.

A body with no identification is found in a local reservoir, and a couple fall victim to a brutal killer in their own home. Frost is assigned a new, female, West Indian detective constable, Ronni Lonnegan, and gets off to a bad start with a few racially-insensitive remarks. He then reluctantly accepts the help of a psychological profiler, psychiatrist Pam Hartley, who he met at a conference. Meanwhile, there is an inspection of Denton Police underway, and Frost's old-fashioned methods are not endearing him to the inspector, so Supt Mullett is forced to give him more support than usual.

Nursing his terminally-ill wife, Det Insp ""Jack"" Frost's life becomes more stressed when, during a missing-child investigation, he unearths evidence on a 30-year-old case involving a skeleton chained to a locked strongbox that turns out to be empty.

Frost investigates the murder of a teenage girl, and the case of a woman who has been receiving threatening phone calls. Meanwhile, at the Denton police station, there are threats, deaths, arson and a staff shortage.

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 continues to try to identify the detective's killer. The task is complicated by a bizarre series of pet shootings, about which he is reluctantly forced to seek help from a computer system run by a seconded new junior WPC. His pursuit leads to a confrontation high above a power station.

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.

A woman is found in a critical condition in a quiet village on the outskirts of Denton, a victim of an apparent hit-and-run incident. Her husband and daughter are distraught. Frost's investigation exposes the secret life of a corner of rural England.