Slow Horses season 5 episode 1 ending explained: Why did Rob Trew carry out the mass shooting?

The explosive return of Apple TV+’s hit spy thriller sees Slow Horses season 5 episode 1 kick off with an unsettling bang. Adapted from Mick Herron’s London Rules, the show once again throws the misfit agents of Slough House into a world of conspiracies, cover-ups, and hidden agendas. This time, the story begins with an orchestrated mass shooting in a busy shopping center, instantly establishing the dark political tone that defines the season. 

While Jackson Lamb continues to corral his team of flawed but skilled agents, the narrative highlights the messy overlap between personal grief, government bureaucracy, and calculated violence. With the scars of the previous season still fresh, the premiere blends tragedy, suspicion, and shocking betrayal, culminating in a chilling ending that asks one pressing question: What really drove Rob Trew to such an act, and why was he silenced before answers could surface?

What the ending of Episode 1 reveals about Rob Trew’s motives

The final act of Slow Horses season 5 episode 1 confirms that Rob Trew, the man behind the Abbotsfield Shopping Centre attack, was not simply a lone wolf. His rampage, which left 11 dead, initially appeared to be politically motivated. At his apartment, investigators found books by far-right candidate Dennis Gimball and a photo of Trew with the politician, suggesting that his actions were influenced by extremist rhetoric.

However, the brutal twist comes when Trew is executed mid-attack by a sniper — someone working with the very group that supplied him with weapons.

This raises the possibility that Trew was a pawn. His connection to The Unseen, an online forum for disaffected men, deepens the suspicion. There, he frequently posted about misogyny, cultural resentment, and a belief that his British identity was under attack. A user named “Sniper762” goaded him into action, providing encouragement and possibly resources. The chilling detail— that the sniper who killed Trew used a 7.62 caliber bullet— ties the manipulation full circle. Trew may have believed he was making a political statement, but the ending reveals he was set up as disposable, a puppet in a larger, shadowy operation with far-reaching consequences.

Recap of Slow Horses Season 5 Episode 1

Beyond the mass shooting, Slow Horses season 5 episode 1 offers a sharp look at how the Slough House agents are coping after the blood-soaked events of season 4. Shirley Dander remains rattled by Marcus Longridge’s death and is convinced the mysterious white van that nearly killed Roddy Ho is part of a broader plot. Though dismissed by most, her instincts align with evidence that the same van was tied to the sniper’s escape.

The personal stakes intertwine with the larger political drama. Catherine Standish maintains her steady, empathetic presence, while Jackson Lamb keeps his cards close to his chest.

The arrival of Emma Flyte at the crime scene underscores the tense relationship between MI5’s tactical wing and Slough House’s castaways. Her discovery of the sniper’s nest and the bullet casing shows that whoever orchestrated the shooting wanted MI5 to know they were dealing with professionals.

By the episode’s end, suspicion and paranoia ripple across London. Shirley’s gut feeling about threats against Slough House agents appears justified, as Roddy’s new girlfriend secretly reports on his movements. With the body count rising, political leaders panicking ahead of mayoral elections, and MI5 caught in a web of half-truths, the stage is set for a season steeped in manipulation, betrayal, and deadly cat-and-mouse games.

The ending of Slow Horses season 5 episode 1 makes it clear that Rob Trew’s mass shooting was never just about his personal anger or extremist beliefs. Instead, he was baited, armed, and ultimately silenced by forces with larger political aims. His execution by a sniper reveals that he was both a weapon and a scapegoat, sacrificed to protect a deeper conspiracy.

For Slough House, the fallout promises a season filled with mistrust, hidden agendas, and questions of who truly controls the game.