A group of animal-rights activists has threatened a series of assaults on London, and a petrol bomb attack leaves the 10-year-old daughter of a commercial lab owner critically ill in hospital, as the time-travelling police drama set in the Eighties continues.

DCI Gene Hunt is outraged at the maiming of an innocent child and gives DI Alex Drake and the team strict orders not to sleep until the culprits have been brought to justice.

Gene and Alex’s first stop is a prison where known animal-rights campaigner, Robin Elliot, is serving time for killing a scientist. Robin is extremely weak from a hunger strike and, although he has had no contact with the outside world for 10 years, Alex is convinced he knows about the planned attacks. His seemingly incoherent ramblings also shock Alex when she realises that he may know about her situation and be able to help her get back to her own time.

Realising they are short on leads, the team trawl through Robin’s past and visit his old lodger, Jeremy, now a respectable psychoanalyst. Jeremy agrees to help with the investigation as the team race against time to find out where the next attack will take place.

Meanwhile, Gene is drawn deeper into the web of corruption weaving its way through the force. He and right hand men, DS Ray Carling and DC Chris Skelton, are shocked when Supermac threatens to relocate Gene to Plymouth. Gene is fighting for his career, Alex is fighting for her life, could it be they’re both fighting losing battles?

Bank Holiday Monday 4 May
9.00-10.00pm BBC ONE