It's a thin line between revenege and murder. . .

To the public, he's a hero: a killer who targets convicted paedophiles.

Two men have already been tortured to death and, for the police, their cases are not a priority.

But DC Maeve Kerrigan believes that no one should be allowed to take the law into their own hands.

As the killer's violence begins to escalate, Maeve is forced to confront exactly how far she's prepared to go to ensure justice is served...