A John Doe is found months after his death; an attractive female agent for a championship athlete is believed to have jumped to her death from a rooftop. Forensic pathologists must sort out time and methods of death.

Sam Ryan steals a toothbrush to get the DNA of the father of the unborn child of a suspected suicide. Tangled relationships between an athlete and his family are amplified when his body is found hanging in her apartment. Police arrest the athlete's brother-in-law after an anonymous tip. Harry's attempts at determining time of death by the growth of maggots give a wrong answer.

The team is called in to identify the corpse of a woman whose face was surgically removed after death. Janet Mander, a Home Office anthropologist, cannot link it to similar murders but, after Nikki has reconstructed the face, Holly, a medical student on work experience with Harry,recognizes the woman as Fran Price, an investigative journalist. Pargeter, her agent, is evasive and Supt. Barker, the investigating police officer, does not help as he is obsessed with the idea that Leonid Polyak, a Russian criminal Fran helped to put behind bars, has ordered a hit on her from his prison cell. Whilst Leo gets closer to Janet, Harry is concerned when he sees Barker entering Holly's flat and later she is found murdered in her bed.

Everyone is affected by Holly Farr's murder. The pathologists find that she was tortured and beaten but died from having her throat slit. The police believe that her death is related to that of Fran Price and the recent leaks of forensic evidence to the press may have led the killer to her. Supt. Barker decides to put armed policeman to guard each of the three pathologists but Harry Cunningham, who saw Barker go into Holly's house, is suspicious of his true motives. When a prominent Russian, Oleg Kolik, seeks asylum in the UK saying he is the true target of the Russian assassins, Harry thinks that Fran Price may have been targeting him in her new book. When Leonid Polyak is murdered while being transferred between prisons, he decides it's time to put his job on the line in the pursuit of justice.

Harry Cunningham investigates the death of a young Orthodox Jew. He accedes to the family's request that he not use invasive procedures in his examination and finds that the young man was savagely kicked and beaten to death. DI McKenzie has a suspect in custody but from what medical and forensic evidence Harry is able to find, with Nikki Alexander's assistance, it's obvious that the family is lying about the young man's whereabouts the night he was killed. Leo Dalton meanwhile investigates the death of a young student who died from a drug overdose. Leo is uncomfortable with what he finds, particularly that she had sex with one of the men at a party when her boyfriend was in the next room. He thinks she may have been given GHB.

With a second member of the Orthodox Jewish community dead, Harry performs a complete examination. This time, Harry does not hesitate to use all examination methods at his disposal and finds forensic evidence that clearly links a third member of the Hassidic community to both deaths. After DI MacKenzie makes the arrest however, Harry realizes he may have inadvertently contaminated the DNA evidence leading to a false result. Nikki retests all of the evidence and together they figure just who the attacker was. Leo Dalton meanwhile tries to prove that the dead student had been given GHB. He concludes that someone also tried to administer CPR.

Insurance investigator William Byfield is found gassed in his car after he has sparred with Nikki over a claim for terminally-ill suicide Sally Craven. He was also perturbed about the suspicious death of one Stephen Connelly, which leads to Leo being accused of falsifying the post mortem by William's successor, Clare Ambler. In fact Connelly's details never reached Leo and his widow, bereavement counsellor Rebecca, is not only uncooperative with Clare but is Harry's current girl-friend and overly friendly with coroner's officer David Levin. When it appears that William Byfield was murdered Harry suspects Rebecca of being involved.

Now Leo is under investigation by the police over the discrepancies in Stephen Connelly's file. He think he's found the solution when he notices similarities between the Coroner's file on Connelly and another case he had worked on. Harry is convinced that his new lover Rebecca, Connelly's widow, has nothing to do with the apparent forgeries Leo has found. He believes that the fraud is taking place at the Coroner's office and focuses on David Levin, who had access to the information. After Leo is assaulted outside his home, he is hospitalized and in a coma. On the edge of death, Nikki and Harry learn they may have a major decision to make. When the police find Leo's blood in Rebecca Connelly's home and Levin's body in the boot of her car, they are convinced they have the killer. No one however realizes the true deception that is taking place.

Ruth Gardiner falls to her death from a squat in a high-rise block and Leo - unlike D.I. Neill - realises that she was murdered though Neill seems reluctant to launch a public appeal. Ruth's father tells Leo she left home two years earlier, he assumes to join a cult, but had phoned recently to say she was retuning to him.Reading of the death car salesman Phil tells his girlfriend Danielle that he is an undercover cop working with Ruth - who was staking out a resident in the flats. Danielle meets with Leo, telling him Neill is corrupt and anxious to shut down Phil's operation,which is to expose sex trafficking. Phil - real name Peter Carmody - takes Alex Webb, an apparent suspect,to a caravan where he will be safe. Harry, meanwhile, discovers that a recently deceased family friend had had an affair with his mother.

Carmody goes on the run and Danielle is killed. The same man's DNA is found in her flat as on Ruth's corpse. Leo's partner Janet persuades him that Neill is not dishonest and Neill discovers that Carmody is a car salesman working with Webb. A failed police college entrant some years ago, he has persuaded his wife and mother - as well as Ruth,Danielle and Webb - he is an undercover cop though when Janet interviews his mother she says that he was a fantasist since childhood. Clearly he is a loose cannon, rubbing out those who discover his secret and must be found. Harry discovers that his father was a bully, driving his mother to having an affair.

The team attend at the apparent suicide of student Jason Renfrew at the local university. The Dean tells Leo Jason complained to her about racist bullying and he is found to have swallowed a chip containing photos of the alleged bullies, as well as having a handgun in his locker. Soon afterwards a gunman goes on the rampage, killing several people including the policeman investigating Jason's death. Nikki and Harry are trapped in a classroom with some students, one of whom, the mortally wounded Matt Frisk, was one of Jason's tormentors. Commander Somerville leads the police team who release them though it is Harry who finds the severely injured gunman. However, he fails to spot the bomb planted on campus.

Nikki's archaeologist friend Patrick is excited when a woman's body,apparently a thousand years old,is unearthed on a Yorkshire moor. However dental records show she is a more recent murder victim and Leo,who once worked in the area,believes she is Jodie Fisher,who went missing in 1985. Three other girls were murdered and the killer,Karl Bentley,caught and jailed. Leo,unsuccessful in his efforts with Janet to make a baby and applying to adopt,reencounters Jodie's mother,old flame Carol,before visiting Bentley,who creepily says that his actions were 'out of love'. Then another woman is killed.

Janet travels to Yorkshire with Leo where she identifies the murder of the fresh victim,Kelly Summers,as being a copycat of the Bentley killings,suggesting that Bentley had an accomplice still at large. This is confirmed when Sonia Hardwick,the investigating officer,finds a letter to Bentley from a boyfriend in the original file. A television crew visits the Fosters' farm house,where Carol's husband Bill snaps,attacking a journalist. He is arrested and interviewed by Sonia regarding his relationship with Karl Bentley. Between them Sonia and Leo deduce that Bentley had a male lover responsible for the unsolved murders and that that man is Bill Fisher. They are only partly right. Harry,meanwhile,has to baby-sit the teenage son of an irresponsible old college friend.

Following the suicide of colleague Lizzie Fraser, who he believes was scapegoated by police for a wrong decision, Leo comes to work in an angry, bitter mood. DI Connie James brings Leo, Harry and Nikki in following the brutal slaying of ex-SAS soldier Mick Francis, his daughter Jessie, and her young son Luke at their farm shop during a robbery. Harry establishes a good rapport with the pregnant Connie but then Superintendent Byrne links the murders to that of Lizzie's sister Mary twelve years earlier and to several other unsolved murders in the intervening years. Byrne believes the killer is a drug-addicted woman known as the Wraith, working with a male accomplice. However unknown to him a hooded white boy who was at the shop would seem to fit the bill.

An eye witness account and identification of a car links a youth called Lee Ness to the farm shop murders but he claims not to know the Wraith. Tom Byrne,recently widowed,and Nikki,who has just lost her father,develop a rapport whilst interviewing the parents of another supposed victim of the Wraith,who have their own views on the murderer's identity. A discrepancy in the findings of the Wraith's DNA at different crime scenes leads Harry to take samples from a rival laboratory. The result reveals an elaborately plotted revenge scenario to punish the police for the deaths of Mary and Lizzie.

Prison inspector Rachel Kruger is murdered,along with young Nick Owen,a man she was visiting,whose computer is stolen.Inspector Bridges tells Leo she reckons Rachel's husband Peter killed his wife and her suspected lover but Peter claims that Rachel was in danger because she was investigating sinister events at Redhill prison,particularly the mysterious death of convict James Wade,and Leo believes him. The team joins the police investigation of Redhill,where governor Cairns is less than helpful and Rachel's original source,Dr Ross,too scared to speak out. But, unbeknown to the pathologists, Bridges knows far more than she is letting on.

When prison officer Ellis Roberts and convict Benjamin Johnson are killed after a supposed cell fight Leo is suspicious of corrupt officer Kessler,whose evidence about the fight does not ring true and is found to have fathered a child with Andrea Bridges before he left the police under a cloud. Nikki persuades Bridges to confess that she covered for Kessler in the past but,despite Kessler visiting Leo to threaten him,there is doubt that he murdered James Wade and the prison inspectors Kruger and Owen. The eventual discovery of the truth spells bitterness for both Leo,ending his relationship with Janet,and Harry.