Episode 1

A teenage boy stands outside an inner-city flat block with a holdall of guns and a phone camera trained on him. He aims the pistol at one friend, changes his mind, and turns it on a passing cat, machine-gunning it while the other boy films and laughs. The cruelty opens series 4 and introduces Wayne (Barry Keoghan), who then announces he has to kill someone: the gang boss Nidge (Tom Vaughan-Lawlor). The camera cuts to Nidge watching pornography alone in the dark, and the cat is never mentioned on screen again.

Nidge visits Darren Treacy's grave, and Darren's body also lies on a mortuary slab, killed at the end of series 3. Tommy (Killian Scott), left brain-damaged by Nidge's beating, sleeps beside his partner Siobhán (Charlie Murphy) as blood seeps from his ear. Nidge, Fran (Peter Coonan), Ado and Elmo (Laurence Kinlan) plan a tiger kidnapping of a cash-in-transit driver, and when one of their drivers drops out Nidge brings Tommy onto the team over Fran's objection, reasoning that the plate in his skull makes him effectively bulletproof.

The crew take a cash-van driver's wife and two daughters hostage in their home, Fran in a demon mask. Inside, Tommy lifts his balaclava to scratch his face and lets the elder daughter see him; later he lets her get away and Fran chases her. The plan collapses when the driver's colleague refuses to cooperate and calls the Gardaí, so Nidge and Elmo take the money on the spot, move the cash into another car, and burn out the getaway van with Fran's mask inside.

Elsewhere, Andrew (Peter O'Meara), a dentist who cannot pay his brothel tab, is pressed by Nidge into importing a large drugs consignment through his practice. Tommy returns to the hostage family's house to check on them and is arrested. That brings in D.I. Mick Moynihan (Brían F. O'Byrne), who runs an undercover surveillance operation and sees in the vulnerable Tommy and the anxious Siobhán a way into the gang; he offers Siobhán a word to a judge for Tommy in exchange for her cooperation. The hour ends where it began, at Darren's grave.

The episode's strength is its opening: one act of casual violence sets the colder tone, introduces the new antagonist and gives the run its most remembered image before the title sequence. Its real weakness, flagged later by the Irish Times, is that the contest between Nidge and Moynihan was never sustained, because the police characters were thinly drawn; the promise of this hour is not paid off.

It is also the structural turning point of the series. For the first time the Gardaí are pulled from the margins into a genuine parallel story with a command of their own, adding a procedural spine to a show that until now ran on gang betrayal alone. It re-centres everything on Nidge by killing the original protagonist off screen before the action starts, and it hands Barry Keoghan his first credited screen role.

The opener drew 970,600 viewers, then the series' largest audience, and criticism was largely warm: the Irish Times called it a taut, emotionally draining hour that lived up to the hype. It also produced the run's biggest complaint wave, over the cat. RTÉ confirmed 41 complaints, 32 written and nine by phone, by 8 October, four days after transmission on 6 October. By the finale the broadcaster's cumulative figure, given to the Irish Independent, had risen to 91 emails and 27 calls about the cat, plus three emails about dog fighting. The two counts are a running total rather than a disagreement, with Wikipedia's over a hundred at the top of the progression. The Animal Rights Action Network called for a boycott and the ISPCA said the scene sparked outrage, but RTÉ confirmed no animal was harmed: the cat was led on a fishing line under an experienced handler, the line and the blood were handled in post-production, and the animal was given an anaesthetic by a vet.