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.

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.