Slow Horses Season 4 Ending Explained: Major Spoilers & Season 5 Predictions

Get ready for a wild ride with Slow Horses season 4! This spy thriller on Apple TV+ brings back all the twists and turns you've come to expect. But be warned: there are major spoilers ahead!

The Final Showdown: Frank Harkness vs. River Cartwright

The season finale throws River Cartwright (Jack Lowden) and Frank Harkness (Hugo Weaving) into a face-off for the ages. After Patrice (Tom Wozniczka) frees River from Emma Flyte (Ruth Bradley), father and son finally confront each other. Frank tries to lure River into his mercenary world, but River reveals the extent of Frank's years-long scheme of creating child soldiers at Les Arbres. This clash sets the stage for an intense cat-and-mouse game across the city.

Also Read: Slow Horses Season 4: New Cast Member Tom Brooke's Character Shakes Up the Team

MI5's Dirty Secrets Exposed

Jack Lowden as River looking concerned in Slow Horses season 4 episode 2 with a still of the compound behind him Image

James Whelan (James Callis), MI5's perpetually incompetent First Desk, issues a "shoot to kill" order for both Frank and River. This order creates chaos as Louisa Guy (Rosalind Eleazar) and Flyte try to arrest Frank, leading to a nail-biting chase and a tense confrontation. Frank, however, is prepared. His ultimate plan is to expose decades of MI5's involvement with his assassination squad if they don't release him. This puts Diana Taverner (Kristin Scott Thomas) in an impossible position – comply or face an agency-wide scandal.

Also Read: Slow Horses: The Truth About Slough House and its Connection to MI5

The Slough House Showdown and a Tragic Loss

A composite image of River looking on in shock in front of Dander and Roddy using a computer in Slow Horses Image

While River battles his father, a dangerous situation erupts at Slough House. Patrice, armed with information obtained from Sam Chapman's (Sean Gilder) stolen phone, attacks the office. Marcus Longridge (Kadiff Kirwan), tragically, becomes a hero as he makes the ultimate sacrifice to protect David Cartwright (Jonathan Pryce), River's grandfather. His death highlights the risks these agents constantly face.

Also Read: Slow Horses Season 4: What's in Store for the Apple TV+ Spy Thriller

River's Choice and Family Drama

Gary Oldman as Jackson Lamb eating ice cream in the season 3 finale of Slow Horses Image

The fallout from these shocking events forces River to confront his grandfather's failing health and their complex family dynamics. In a poignant scene, he keeps a promise to Louisa, finally securing proper care for David in a residential facility. Though David initially resents this, River remains steadfast. This decision highlights the evolving relationships among the main characters and shows River's growing maturity amidst extraordinary circumstances.

Also Read: Slow Horses Season 4: River Cartwright's Shocking Fate

Moira's Revenge and Whelan's Downfall

Moira Tregorian (Joanna Scanlan), always one for a little payback, finally gets hers! Her investigation into the forces who banished her to Slough House leads her to expose Whelan's (James Callis) shady past—specifically his misuse of his position during his time as a metropolitan police officer. Using this unearthed secret, Moira negotiates for her return to a higher position within MI5 with a generous pay rise, suggesting further conflict and consequences within the organization.

The Future of Slow Horses

Season 4's ending sets up intriguing storylines for season 5. With Frank Harkness seemingly alive, and Whelan's continued incompetence highlighted, it looks like there is plenty more excitement for the next series!

Expect more turmoil for MI5 as the series expands upon the novels of Mick Herron's "London Rules." Season 5 will potentially show us just how much longer the agency can continue covering up their numerous failures while also allowing the characters and their relationship to have a chance to move into new territories.

The Slow Horses cast looks to continue making waves as Gary Oldman will hopefully continue in his role, leaving viewers excited to continue with the series. Apple TV+ gives its audience yet another wild ride!