Nikki and Harry try to help wounded victims of a campus shooting while trapped in the building with the rampaging shooter.

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.

Leo's postmortem of the victims reveals there were two guns used, and possibly a second shooter.

Leo investigates a potential copycat killing, but the team are starting to wonder if Karl Bentley was wrongly convicted, leaving the real murderer free to set out on a new killing spree.

A family murdered at a picnic leads the team to the female victim's estranged husband.

As Nikki and Jack move closer to the truth, their lives are thrown into mortal danger.

As the search for Liam continues, Nikki's loyalty towards her former mentor is tested.

When arrested and interrogated by DI Kate Warren, Alan Lane vehemently protests his innocence and insists he didn't kill his wife.

Nikki and Jack investigate links between the victims to close the net on the killer.

Nikki helps high-flying DI Luke Nelson unearth painful childhood memories.

When a woman’s body is removed from a reservoir, Nikki performs the post-mortem and confirms she is the deceased wife of pathologist Charles Beck. Jack and Velvy discover new evidence that leads to a surprising arrest as Nikki continues to seek the truth about notorious serial killer Calvin Dunn.

The Lyell are called to a museum outside King’s Cross Station, where they discover the bodies of eight victims entombed below. With the knowledge that a prolific serial killer was operating in London nearly twenty years ago, Nikki and the team know this will be a case like no other.

When a mysterious contagion starts to spread on a flight from Mumbai, Dr Nikki Alexander faces a race against time - at 30,000 feet - to contain a deadly illness.

When a pub landlady is stabbed to death and her little finger cut off, Nikki is isolated in her quest to prove the husband's innocence.

Conflict brews between Leo and Nikki when he suspects her new boyfriend is involved in a 50-year cover-up, leaving Leo battling alone to expose the truth.

Nikki and Jack strive to track down a sniper at large in London and stem a public crisis.

Nikki and Jack investigate a man killed by a train on the London underground.

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.

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.

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.

Nikki continues to try and identify the last of the remaining bodies in an effort to uncover any connections and find motive, while Jack and the police begin to look into several two-decade old missing persons cases which might reveal the identity of the man dubbed “The King’s Cross Serial Killer”.

When more passengers become infected on the plane, Nikki and the Lyell team must work to uncover the truth and find a cure before it’s too late.

Sam learns that the captain of the helicopter died of a heart attack, but she doesn't think it was the cause of the crash, and with 75 helicopters grounded, accident investigator Tony Newsome needs some answers.

Leo, Harry and Nikki step up their efforts to discover the truth behind the train crash but there are still many unanswered questions.