Slow Horses Season 3 Might End With A Major Cliffhanger

Based on author Mick Herron’s 2016 Real Tigers novel, Apple TV+’s Slow Horses Season 3 centers on a romantic liaison in Istanbul that threatens to expose a buried MI5 secret in London. Soon, Jackson Lamb (Gary Oldman) and his team of British intelligence misfits are caught in a conspiracy that threatens the futures of both Slough House and MI5 itself.

Though the espionage drama’s first season was “very faithful to the plot of the original book,” as Herron put it to Radio Times in 2022, he’s given his blessing for subsequent installments to deviate from the source material.

“All the big changes to plots have been made with either my happy agreement or, sometimes, at my suggestion,” the author said, noting he wanted the adaptation to preserve “the characters and the tone, which elides between comedy and sometimes tragedy.”

While the Apple TV+ series might play out differently, here’s a brief summary of the Real Tigers plot and ending.

A Kidnapping Caper

The action in Real Tigers — the third of eight novels in Herron’s Slough House series — kicks off when Lamb’s assistant, Catherine Standish, is abducted by her ex-lover, Sean Donovan, and held for ransom outside London. In exchange for Catherine’s safety, the kidnappers demand that fellow “slow horse” River Cartwright infiltrate MI5’s intelligence headquarters, Regent’s Park, and retrieve a secret intelligence file.

It turns out the kidnappers are a “tiger team” testing MI5 security for Home Secretary Peter Judd, but then, they go rogue and kill Donovan’s boss, Sly Monteith. Once they take control, they change the ransom demand to the retrieval of a different top-secret file from another location for unknown reasons.

A Deadly Government Conspiracy

The plot also follows the rivalry between MI5’s First and Second Desks, Ingrid Tearney and Diana “Di” Taverner, two of the most powerful women in the UK intelligence community. It’s revealed that Judd and Taverner are working together on a plot to oust Tearney by exposing the secret prisons in the Project Waterproof files.

Though Lamb and Roderick “Roddy” Ho rescue Standish, no one’s safe when Tearney learns of the scheme and orders Nick Duffy and the Black Arrow mercenaries to kill the slow horses and others with knowledge that could implicate her.

The Slough House team survives, but casualties from the attack include Donovan, who’d aligned with Slough House, Ben Traynor, and several Black Arrows. Cartwright also knocks Duffy unconscious with a metal pipe, leaving him with “limited brain function,” while saving Marcus Longridge’s life.

The Final Chapter

In Real Tigers’ final chapter, Lamb meets with Taverner on a park bench. They discuss the deaths, and Lamb also recounts how Standish quit Slough House after he harshly told her that her revered former boss, Charles Partner, who she believed died by suicide, was selling government secrets to the Russians and only hired her because she was an alcoholic and wouldn’t be alert enough to catch on to his scheme.

Lamb has the folder containing the Project Waterproof files, and Taverner predicts that, if handled internally, Judd would encourage Tearney to retire, leaving a vacancy for her to head M15. She would then help Judd become Prime Minister. The only problem is that Lamb is the one with the evidence and mentions he could easily leak it to the press publicly.

He hands over the folder to her anyway, but after he walks away, Taverner discovers the files are missing. Real Tigers’ final line of dialogue is her calling Judd to let him know their “worst-case outcome” just happened.

Even More Cliffhangers

The book’s final pages also reveal that Cartwright inexplicably paid a visit to James “Spider” Webb’s bedside, only to find it vacant. He has “queasy suspicion” that his lie to Taverner about Webb not wanting to be on life support might have produced an “unintended consequence.” However, the novel intentionally leaves open-ended whether or not Webb is still alive somewhere or if Taverner actually pulled the plug.

Meanwhile, Judd sends his assassin, Seb, to murder Lamb and retrieve the Project Waterproof documents. While pretending to be asleep, Lamb is ready and kills Seb, leaving his slow horses to dispose of the body.