When a boat carrying illegal passengers is found crashed in the Thames, the team investigate.

The team follows the trail of the people traffickers, and has to find any remaining survivors before a highly contagious disease breaks.

The team investigates a hit-and-run accident, an arson and a woman who collapsed on her hen night.

The team investigate a man who died on a night bus, an office prank gone tragically wrong and the suicide of a pro footballer.

Harry and Nikki's friendship is rocked by the discovery of the body of Harry's ex-lover.

Memories of his own daughter's death are stirred up when Leo is called in to investigate the suicide of a 14-year-old girl.

Memories of his own daughter's death are stirred up when Leo is called in to investigate the apparent suicide of a teenage girl.

When a third killing takes place on school grounds, Leo races to find some connection between the apparently motiveless murders.

Harry and Nikki are drawn into a war between a medical research establishment and a group determined to take direct action.

With Nikki missing, Harry works against the clock to find out who is responsible for the murders and finds himself in a cover-up.

Harry and Nikki are first on the scene when an RAF helicopter crashes, but Harry's search for answers brings him into conflict with the Ministry of Defence.

Harry suspects the Ministry of Defence may be covering up the true cause of the helicopter crash, but he's determined to get to the truth.

When the mutilated body of a young boy is pulled from the river, Leo is determined to give him an identity and to bring his killers to justice.

Leo refuses to back down in his search for the killers of the young boy, despite threats and increasing racial tension.

The murder of a John Doe leads the team to a hospital, where Nikki is investigating a top paediatric surgeon with an unusually high mortality rate.

With Nikki out of action and Alice's surgical team closing ranks, Harry and Leo dig deeper.

Nikki revisits an emotive case from the past when a girl she proved innocent of murder is herself murdered.

Nikki grows increasingly worried that a mistake she made on a case four years ago may have contributed to the murder of a young woman.

When the bones of a young girl are found, everyone but Nikki is convinced it's a teenager who went missing two years ago.

Having fallen out both with both the police and Clara's family, Nikki finds herself increasingly alone in her search for the killer.

Nikki arrives at a murder scene to find it's a carbon copy of a case in her past.

Nikki becomes the prime suspect after a former colleague is murdered.

A young British Muslim returns to the UK, and concerns over her intentions soon escalate.

Thomas must put his personal feelings aside as the team track down Begovic.

An ex-convict is killed and suspicion lands on a recently released child killer.

Further victims are killed and a distinctive modus operandi begins to become clear.

The shooting of a teenager in an armed police operation triggers a series of murders.

Jack leads the hunt for suspected killer Bruno, the brother of the shot teenager.

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.