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.

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.

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

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.

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.

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.