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

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

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

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.

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

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

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

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

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