Leo is stopped for drink driving and finds himself doing community service in a rough part of South London, in the opening story of the 12th series of the medical crime-drama. He has to answer to a tough-talking community worker, AJ, who’s not pleased that he’s been assigned a “drunk whitey”. The kids laugh at Leo behind his back, trying to intimidate him. It is an unsettling experience and he keeps his mouth shut.

Elsewhere in South London, Nikki is called out to a funfair at a local park where a teenage girl has fallen to her death from a ride. The paramedic, Ryan McBride, is more interested in Nikki and doesn’t waste any time in asking her out. She focuses on the job in hand, but doesn’t say “no”. Upon closer inspection, Nikki begins to suspect that the girl may have already been injured when she was strapped into the ride. The site is quickly turned into a crime scene.

The post mortem confirms that the girl had been stabbed. It also reveals that she may have been brutally raped. DS Wallace, the investigating officer, suspects that the rape may have been part of a gang initiation. One of these gangs is headed up by Keenan, who is trying to recruit Levi – one of the young boys from AJ’s youth club. Leiv’s older brother, Errol, used to “run” with Keenan’s crew.

Leo tries to keep his head down, he just wants to do his hours and get out. But when Errol is stabbed near their playing fields, Leo steps in and takes charge, much to AJ’s surprise. Leo’s quick, decisive action wins him new respect from AJ and the kids, particularly Levi.

Wednesday 1 October
9.00-10.00pm BBC ONE