“In the criminal justice system, the police investigate crime, and the Crown Prosecution Service prosecute the offenders.” But it’s not always that straightforward. How are the police and lawyers supposed to react when the most awful crime imaginable – the murder of a child – is committed by killers who are just children themselves? That’s the case that launches the third series of this British adaptation of the powerful American series. It’s a gut-wrenching episode that will shock viewers and bring inevitable comparisons to the horrific, real-life murder in 1993 of toddler James Bulger.

DS Ronnie Brooks (Bradley Walsh) and DS Matt Devlin (Jamie Bamber) are faced with the murder of little Conor, who has been strangled. That’s sickening enough, but there’s also irrefutable evidence that the little lad was killed by two children: CCTV footage that shows the innocent, trusting toddler being led to his death by his young killers. The two children arrested blame each other. But is this because they’re scared of the consequences? Or are they trying to be cunning?

CPS Director George Castle (Bill Paterson) realises his department is being watched very closely by his bosses and by the public, but he makes a decision that shocks everyone: he turns to the victim’s mother, whose point of view surprises everyone.