How Slow Horses Season 3 completely changed Sean Donovan's story from the books (& not for good)

Slow Horses might be one of Apple TV+'s most faithful book adaptations. However, Season 3 made one significant deviation that's still being debated by fans. Sean Donovan's story was altered, and the opinions are divided.

While the show did retain the rough MI5 world of Mick Herron's Slough House novels, Season 3 altered Donovan's arc into something much more tragic and, arguably, far less complex.

In the books, his guilt and grief all feel earned. However, on-screen, his story feels utterly uncomplicated. This shift changes everything about how we understand the character in Slow Horses.

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Reconstructing Sean Donovan: When TV traded tragedy for sympathy

In Mick Herron's Real Tigers, Sean Donovan is a man already broken before the story even begins. Recently released from prison after accidentally killing his partner, Alison Dunn, in a drunk driving incident, his pain feels real. That guilt shapes every decision he makes.

But Slow Horses Season 3 decided to wipe off that tragedy clean. Instead of being her accidental killer, the show paints Donovan (played by Sope Dirísù) as a man desperately seeking justice for Alison's death, not redemption for causing it.

This small change transforms his entire character. On TV, Donovan becomes a straightforward avenger, heartbroken over a murder committed by someone else and not him. In Herron's version, he's both the victim and the villain. He was someone who unintentionally did something terrible, and he can't forgive himself for it.

That moral messiness is gone from the show. Series creator Will Smith explained this creative decision to Radio Times, saying;

"It works in the book because you can go in his head... but on TV, you need to see that love and grief."

The team wanted to make Donovan's motivation visual, so that the audience could feel it, not just read about it.

But while that choice makes sense for television, it also strips away one of the story's most haunting elements: Self-inflicted guilt. Herron's Donovan is a man haunted by the truth, and someone else's actions haunt Slow Horses' Donovan. That may make him more likable, but it also makes his story less interesting.

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How Slow Horses changed Catherine Standish’s connection and lost emotional depth

The show doesn't just change Donovan's past; it changes his relationships, too, and most importantly, with Catherine Standish. In Real Tigers, Standish isn't just a hostage; she shares a complicated romantic history with Donovan.

They've loved, lost, and suffered, and that emotional baggage makes their reunion all the more charged. Their scenes carry the weight of regret and betrayal, portraying two broken people trying to mend something that cannot be fixed.

On Slow Horses, that layered connection disappears. Donovan and Standish (Saskia Reeves) meet for the first time in an Alcoholics Anonymous meeting. There's no shared past, no messy history, just a forced alliance between strangers.

Donovan kidnaps her to use as leverage against MI5, but instead of tension, we get sympathy. Standish grows to understand his pain, even helping him in his pursuit of the Footprint file—a top-secret document containing MI5's most sensitive secrets.

In Herron's version, their bond is the emotional core. It's messy, human, and full of moral contradictions, which is precisely what Slow Horses usually does best. By erasing that shared past, the show trades emotional complexity for simplicity. And that's the real loss.

The dynamic between Donovan and Standish in the book reveals how guilt, love, and loyalty can twist together in dangerous ways. The show, however, flattens those layers into a single note of pity.

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Slow Horses Season 3 still offers a riveting story, but its reexamination of Sean Donovan's character leaves behind what made Mick Herron's writing so powerful: his moral ambiguity. By making the choice to change a guilty man into a grieving one, the show merely simplifies the tragedy of a character into a straightforward, revenge-driven narrative.

It's easier to digest, sure, but somewhere it does lose the emotional edge from the books that made Donovan feel unforgettable.

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