Forensic pathologist Dr. Sam Ryan returns to Cambridge to take up a teaching assignment and to work for the police as required. In her first case, she has to deal with the death of a six year old girl find floating in a nearby river. The autopsy reveals that the child has suffered previous abuse, including cigarette burns and several broken ribs. Sam receives information from a prison inmate that implicates someone in a previous death and Sam suggests a radical step. In her personal life, Sam has to deal with her elderly mother who is showing signs of dementia and her sister Wyn with whom she has a strained relationship.

With the exhumation of a child that had died from abuse some years earlier, Sam is able to demonstrate that there are similarities between the deaths of the two children. There is also only one individual with a connection to both cases. When Sam's house is broken into, her personal safety is a risk but she pursue the case with her usual zeal.

When Mark James' decomposing body is found in an abandoned building, there is every indication that he was part of some occult ritual. An upside down cross was carved on his chest, his wrists were bound with ivy and he was strangled. All evidence points to his friend Sebastian Bird, a rich idler who allowed James to live in his house but who had also developed a expert knowledge of the occult before being sent down from Cambridge for having had an affair with a professor's wife. Sam Ryan's testy relationship with the police continues as she is having difficulty establishing a forensic link in the case and also for publicly criticizing the well-liked Police Surgeon, Dr. Richard Owen, for attending the crime scene without the proper protective clothing. Sam also has to deal with her rebellious nephew Ricky, who is constantly fighting with his mother and announces that he has left home to move in with her.

Sam continues her investigation into Mark James' murder. When another of Sebatian Bird's one-time friends is killed the police are ever more convinced of his guilt and grow increasingly frustrated at Sam's inability to provide them the evidence that they are sure is there. The solution lies in an old case and someone's desperate need for revenge.

Sam investigates the death of a gay man while in police custody. He had been arrested while drunk and was sharing a cell with another drunk, in for the night. The victim died from a blow to the head and was badly beaten post-mortem. DS Farmer is concerned that the assault may have been the work of some of her officers. Sam also meets up with Liam Slattery an old friend she has not seen for 20 years. Sam's sister however is convinced Liam was responsible for the death of their father years before.

Sam continues her investigation in the prisoner's death and believes the police are covering up. When a police constable whose wife reported was cracking up is found dead, the investigating officers themselves believe something is amiss. Sam continues to be harassed by someone unknown and has to call in the bomb squad when she receives a mysterious parcel and subsequently someone tries to run her off the road. Liam and Sam renew their relationship but she is faced with a difficult choice.

One of Sam Ryan's students has a problem and seeks some personal advice. She and her family immigrated from Vietnam during the boat people exodus and her father wants her to enter a marriage he's arranged for her. She's worried that her husband to be will realize she is not a virgin and Sam counsels her that honesty is always the best policy, but in this case it drives the prospective groom to violence. When the family's restaurant is burned out, the police find a badly burned body. On the home front, Sam continues to bicker with her sister Wyn about whether their mother should be placed in a home and the bitterness over their father's death continues to divide them.

DI Adams and DC Cox's personal relationship is now affecting their work, leading Cox to request a transfer. With the burned body now identified through dental records, the police have a suspect. However, he suffers from post traumatic stress disorder and the police are concerned that he may lash out. When the police do finally locate him, a member of the team is killed.

Boxer Kevin Sharma dies from blows received in the ring, but pathologist Sam Ryan determines that he has a brain injury dating from sometime after his last bout two months ago. One of the governors of the boxing board, retired police Superintendent Jack Reeve, is concerned that it will reflect badly on them. Reeve is also trying to cancel one-time trainer Terence Cross' license after he is the victim of a hit and run accident that leaves him a quadriplegic. A new Detective Superintendent, Peter Ross, is now in charge and Sam and he knew each other many years previously. Trevor finds himself alone after his wife leaves him. Sam and her sister Wyn bury their mother

The investigation continues and a boxing trainer apparently commits suicide. Sam isn't convinced however and with the assistance of a ballistics expert, obtains the evidence to prove the suicide was actually murder. She also learns the reason for Kevin Sharma getting into a bare-knuckles fight and now suspects that Terence Cross' hit and run may not have been an accident. Sam's sister Wyn continues to have difficulty coping following the death of their mother.

Stuart Evans is 40 years old and in the advanced stages of AIDS. When he dies the night after his birthday party no one thinks anything of it but his parents donate his remains to scientific study. When Sam and Trevor start an examination of the remains, they notice needle marks and suspect his death may not have been straightforward. Their suspicions are confirmed when the toxicology reports indicate an extremely high level of morphine. Mark Tate is also an AIDS sufferer who has been told that he will soon go blind. He too dies suddenly and when the police learn that he and Evans had the same physician, they begin to suspect doctor-assisted suicide.

As Sam continues her forensic investigation into the two deaths, the police make an arrest but soon realize they have the wrong person in custody when a crucial piece of evidence is uncovered. Sam discovers the true identity of the person behind the deaths but rather than tell the police, she decides to let him to turn himself in. Unfortunately, this leads to a tragic result. In her personal life, Sam and Peter Ross renew their long-ago romance.

Helen Mathews is found strangled on the street. In the course of the investigation, the police learn that she was having an affair with Alan White, a flying instructor working for her husband Michael. From the evidence, it appears that she was about to leave her husband and move to Canada. The police uncover a similar case from several years earlier with a striking resemblance to this case and are convinced that the two must be connected. Friction again develops between Sam Ryan and the police when her forensic analysis demonstrates that the two cases have no connection whatsoever. Sam continues to fret over her decisions in her last case and her personal relationship with Peter Ross reaches a breaking point.

With a second murder on their hands, the police make an arrest in the case. Sam however uncovers some very peculiar bruising on both victims that provides the police with the evidence they need to identify the person responsible. Sam's life is put at risk however when the murderer threatens her. Wyn Ryan, who has been living with Sam since their mother's death, has found a job and is now looking to move on. Sam and Peter continue to struggle with their relationship but are determined to make a go of it.

When 72-year old Millicent Lockwood is found brutally beaten to death in a local park, the police immediately focus on a local who was seen arguing with her a short time earlier. The autopsy reveals little evidence but Sam Ryan once again refuses to make the evidence they do have fit the suspect, which leads to an inevitable clash with the police. She also sees two youths, Kelvin Price and Ben Quayle, act out part of the murder. The police however are pursuing other lines of inquiry and don't have the time, nor the inclination, to pursue Sam's theories. She then sets off on her own investigation.

Convinced that Kelvin and Ben are the murderers, Sam Ryan pursues her own investigation. She is also concerned that one of the boys may do himself harm after a third boy, who was only peripherally involved, hangs himself. The police are concerned that her involvement may actually taint some of the evidence they have and an angry DCI Peter Ross informs her that he has filed a formal complaint with the Coroner and the Chief Constable over her conduct. This obviously affects their professional and personal relationship.

Sam is shaken when she has to look into the death of a very dear friend, Dr. Annabelle Evans, a Cambridge professor. She was found in her home, badly beaten in what appears to be a botched burglary attempt. The police immediately focus on the husband as the likely killer but Sam suspects that an altercation at a local restaurant during the May Ball, where a waiter spilled wine on Annabelle and was fired on the spot, may provide another suspect. Sam is also intrigued by the relationship some of her students may have had with Annabelle, particularly when she learns her friend may have had a lover. In her personal life, Sam has moved on. Her sister Wyn has relocated to Ireland and Peter Ross has also been transferred. She does however run into an old friend who also happens to be an acquaintance of her business partner Trevor.

As Sam, et al continue to look into Annabelle's violent murder, another woman is similarly assaulted.

Sam Ryan looks into the death of Maggie Collins who died of a heroin overdose. Sadly, her body wasn't discovered for several days and in that time, her infant daughter died of dehydration. Soon after Maggie's death Stephen Jackson, a small-time dealer and addict, is killed in an explosion in his home. The autopsy reveals that both of them died of overdoses from the same batch of heroin and Sam begins to doubt that their deaths were accidental. When another small-time dealer is killed, the police think they have either vigilantes or a turf war on their hands. What they have is something far more complex that involves one of their own.

Are the deaths linked to a drug war or to vigilantes?

When Philip Nelson is killed in a farm accident, the pathologists conclude they have a straightforward case of man vs. machine and the machine won. Sam makes an error however and soon finds evidence that points to murder. The police suspect his handyman, all the more so when they discover he was having an affair with Nelson's wife. When the murders continue however, Sam uncovers evidence that connect at least some of the men to events in Northern Ireland when they served in the army together many years before. Sam is more than a little surprised when Charlie, an old friend, sounds her out about taking up a new Chair in Forensic Pathology at London University. DI Michael Connor and his wife take a stab at a reconciliation but he finds it difficult to forgive her infidelity and realizes he has feelings for Sam.

Sam looks for connections between Ian Neal and a killing in Northern Ireland in 1985.