Nikki struggles to come to terms with life back home and seeks out fellow pathologist Sally Vaughan for support, only to learn she is nowhere to be found. National Crime Agency investigator Guy Bernhardt asks Nikki to help him by employing pathologist David Cannon, the chief suspect in Sally's disappearance. As Jack, Clarissa and Thomas share concerns about Nikki's wellbeing, a body found in a reservoir is linked to a murder case from 16 years previously. Return of the crime drama, starring Emilia Fox, with Julian Rhind-Tutt and Alex Macqueen.

Nikki's suspicions about David Cannon are roused further when she discovers blood in the boot of his car an with Thomas's support she takes samples to process. Does it belong to Sally Vaughn? Meanwhile, the uncovering of the body from the 16-year-old murder shines the spotlight on three people who went to the same school. Emilia Fox stars, with Julian Rhind-Tutt and Alex Macqueen.

A series of tragic events are linked to the hacking of a hospital database.

The team wonder if the hack is the only danger as they come under threat.

A US diplomat is shot dead in central London, forcing the team to work closely with the embassy and the FBI.

Nikki is still in shock as the team arrive at Matt's residence but insists on working at the Lyell, determined to help. When analysing crime scene photos and the positions of the victims' bodies, Nikki realises there is a pattern. Together, the team uncover a secret that has been held by those at the very top of the US government.

While two care home staff are chasing Kevin McDowd, a young man with learning disabilities and sociopathic tendencies, Nikki and Jack examine a fatal road accident where the deceased is Kevin McDowd's mother. The investigation led by police sergeant Button should be straightforward, but the forensic evidence suggests foul play.

The team are determined to uncover the truth about unexplained deaths of patients at a care home. They are desperate to rescue Serena and return her to safety. Unbeknownst to her colleagues in the Lyell Centre, Clarissa allows herself to be admitted to the care home in order to investigate. Her determination to find out what happened at the care home leads her to uncover a shocking truth, but puts her life in danger.

Nikki, Jack, Thomas and Clarissa are just settling down for their respective festive celebrations when they are interrupted by a call-out to a tragedy at a family home.

As the truth behind the McMorris family is revealed, the team is brought together by the conclusion of a shocking Christmas family tragedy. Reuniting with their respective families, Nikki finds her secret Santa gift is a visit from a loved one.

Fresh from her trip to the States, Nikki and the Lyell unit are called in to investigate an attack against a trans man. When two further attacks are reported, one leaving a potential witness, it becomes clear that the team is facing an outbreak of violence against the trans community.

A mistake has been made during the course of the investigation, and Thomas is targeted as a scapegoat. As frustration grows between the Lyell and the acting DCI, can Thomas rally the team to gather crucial evidence to find the killer before they strike again?

With new drugs hitting the streets, a head teacher confronts the dealers preying on his community, as the team deal with a surge in drug-related crime.

When tragedy strikes close to home, it puts head teacher Noah Taylor on a collision course with the criminals responsible. Can the Lyell team help him stop the cycle of violence?

A collection of dismembered body parts, covered in intricate Japanese tattoos, have been found in a Brighton waste dump. The team are called in to painstakingly piece them together and they search for clues to lead them to the killer. Outside of the lab, Nikki has some news she desperately wants to share with Matt.

The team struggle to find the final piece of the puzzle left behind by the murders in Brighton. At home, Nikki and Matt discuss their future together.

A car-bomb attack in a quiet suburban street brings back unwelcome memories for Jack, when evidence points to the involvement of a Northern Irish terror group, long thought inactive. As the family of the victim seek their own form of justice, Jack calls an old friend to help them find those responsible and stop the act of revenge from escalating.

During the team’s search for the killer, Jack works alongside an old friend from Northern Ireland, a fearless journalist who has dedicated her life to exposing the suspected organisation. As the team investigate further, they realise they have uncovered a complex conflict sustained by ties of loyalty, family and retribution.

Nikki is humiliated in court when a barrister accuses her of making a serious error in the case of a policeman who may or may not have been murdered. Meanwhile the team investigates the death of a medical researcher found in a canal with mysterious puncture marks on his body.

When Thomas sides against her findings on a controversial case, Nikki suspects foul play and takes steps to prove her theory. Jack and Clarissa follow a forensic trail connecting a dead researcher with a billionaire scientist and a secret testing programme.

The team find unexpected connections between the death of a former US ambassador in a plane crash and the apparent suicide of a successful businessman.

The team discover a connection between the plane crash and a sinister online forum. Meanwhile, Matt is grieving for his friend, putting his relationship with Nikki under strain.

When the body of a missing teenager is found in a field near his village, Nikki and the Lyell team must determine whether the killer is a stranger or a local.

Investigating the murder of missing teenager Jason Forbes, Nikki and the Lyell team are pressured by police officers who are keen to secure a conviction.

A woman's body is found on railway tracks in London. When the post-mortem reveals signs of domestic violence, it brings back troubling memories for Nikki.

When the team's search for Jenny's killer hits a wall, her friends at the women's refuge seek answers. Meanwhile, Thomas makes some friends in high places.

When a skeleton is found in concrete, the Lyell team must investigate a suspicious death dating back 20 years.

The team's investigation leads them to a mysterious cryogenics facility and the discovery of another suspicious death.

Thomas performs a post-mortem on a soldier who died in military training. His investigation takes a turn when he discovers traces of a possible nerve agent.

Jack is rushed to hospital after collapsing at the scene of a car crash. As he fights for his life, the team must identify the poison to save their friend.