There’s something missing in Lewis’s life. It’s not Hobson’s fault, but retirement plainly doesn’t suit him. So when the call comes from Innocent to take up his badge and rejoin the force, he jumps at the chance.

Meanwhile Hathaway (Laurence Fox) is wading into his first murder mystery – a tricky case that bridges the worlds of neurosurgery, blood sports and animal rights. It started with an arson attack on a hunting lodge, but soon enough Hathaway and DS Maddox (Angela Griffin) have a dead neurosurgeon on their hands. Alastair Stoke (Jonny Phillips) was shot in the head on the farmland he co-owned with his troubled business partner Tom Marston (Aden Gillett), but as Hathaway delves into the network of fear and loathing that surrounds the surgeon, the case begins to careen out of control.

What is Alastair's glamorous widow Erica (Kara Tointon) hiding, and what is the nature of her relationship with Alastair’s younger rival in the operating theatre, Simon Eastwood (Leo Staar)? Does the original owner of the farmland, Gillian Fernsby (Anna Carteret), harbour homicidal urges? What of her daughter Lorraine (Elizabeth Rider), Alastair’s loyal scrub nurse, and chippy grandson Chris (Michael Peavoy), a porter at the hospital? What plans does student activist Jessica Tallison (Francesca Zoutewelle) have for Alastair and Tom’s failing business empire?

It soon becomes clear that the case has everything to do with Alastair’s failure to save a badly injured teenager, Nabeel Sira, in the operating theatre; but the hospital staff seem to be closing ranks and the boy’s parents Ayesha (Thusitha Jayasundera) and Rizwan (Ace Bhatti) are considering their options – some of them not entirely legal…

What follows is a second murder, an unfolding tragedy, and the unraveling of a long-running hate campaign… But can Innocent’s experiment – throwing Hathaway and Lewis together again – be sufficient to solve the mystery and stop the killings?