Sam Ryan ayuda a la policía en la investigación de una colisión de múltiples vehículos que resulta en la muerte de 11 personas. Se le unen dos nuevos colegas: el Dr. Leo Dalton, un patólogo experimentado de Sheffield, y el Dr. Harry Cunningham. Mientras intentan determinar las causas del accidente, encuentran un brazo amputado que no pertenece a ninguna de las víctimas. También tienen que lidiar con la DCI Carol Deacon, cuyo papel en la investigación no les queda del todo claro. Sam y Leo tienen enfoques algo diferentes en su trabajo, especialmente en cómo tratan con la policía. Harry realiza su primera autopsia en un niño.

El misterio del brazo cercenado se resuelve en parte cuando la policía descubre un cuerpo flotando en el río con un brazo faltante. Los patólogos continúan su investigación con poca ayuda de la policía y en particular del DCI Deacon. Cuando ella revela a Tom que dos de los hombres en el accidente eran policías encubiertos, él se da cuenta de que Sam tenía razón y que está siendo manipulado. La policía se niega a decirles qué está ocurriendo y la intromisión de Sam tiene graves consecuencias. Harry sigue intentando encontrar un equilibrio entre la distancia y la compasión mientras uno de los sobrevivientes del choque busca su ayuda.

The police investigate an apparent break-in that results in the death of Derek Irons, his wife and youngest daughter. Two older children survived the attack but one is in serious condition and in a coma. Irons was a ruthless businessman who targeted his rivals' customers resulting in regular confrontations. Irons was stabbed but his wife and daughter were shot. Sam is reunited with an old friend from Northern Ireland, Det. Supt. Tony Ashton who is the senior investigative officer on the case. Harry assists the police with the death of an old woman who is believed to have fallen down a staircase. His post-mortem reveals evidence that is not consistent with a fall.

The police continue their investigation into the deaths of several members of the Irons family but based on the forensic evidence, they now believe he may have been killed elsewhere and then transported to his home. When one of Irons' two surviving children is killed, they look to his circle of friends and family for a possible motive. Thanks to Harry's information, the police investigate further into the death of an elderly woman who supposedly fell down the stairs in her home. Supt. Tony Ashton clearly wants to renew his friendship with Sam but she isn't so sure. Leo's home life is in turmoil and it's been affecting his work.

When a decomposed body is found hidden in the wall of an old factory building, Sam Ryan concludes he was murdered. He is eventually identified by his ex-girlfriend Selina Thomson as Marcus Saul, who had simply disappeared one day some seven years earlier. There has also been a break-in on campus and drugs have been stolen. The Dean asks Leo Dalton to speak to some of the students on the issue, but he's not quite sure what he can do.

With the death of a student from a drug overdose, the university must face the wrath of the girl's father, a major benefactor. The autopsy reveals that not only had she taken drugs but also that she had sexual relations with three different men in the previous 48 hours. Although the police have a suspect in the murder of Marcus Saul, new information suggests that the identity of the killer may lie in a completely different direction.