Summary
As perhaps the most important core character inSlow Horses, Jack Lowden’s River Cartwright has been a key narrative focus for three seasons. Although the specifics of his adventures have changed, core aspects of his character have remained consistent throughout. However, following one dramaticdeath inSlow Horsesseason 3, at least one element of River’s story is set to change forever, altering the balance ofSlow Horses' structure and having dramatic implications for its future.
Whether he’s battling far-right extremists, Russian sleeper agents, or internal tiger teams, some things about River Cartwright have not changed.He is, for instance, clearly devoted to his grandfather– a relationship that subtly drives the show’s story forward and will become pivotal inSlow Horsesseason 4. He also has a tempestuous but strong relationship with Jackson Lamb, as well as an important platonic friendship with Louisa Guy. However, these consistencies have not just applied to positive influences on River’s life. Historically, his enemies have also been a fixture – until now.

James ‘Spider’ Webb’s Death Changes River’s Story
Their Rivalry Has Defined Both Men’s Stories
Until his dramatic and shocking death in season 3,James “Spider” Webb was perhaps the biggest enemy River had. As a direct peer, there was always a sense of intense competition between the two – exacerbated by the incident in Stansted airport, in which Webb helped to frame River for incompetence. Ever since, the two have constantly butted heads, with Webb providing an ever-present internal enemy for both River and theentire Slough House team, to the extent that the pair’s enmity leads directly to stories like the tiger team targeting Slough House.
However,Slow Horsesseason 3 has fundamentally changed this picture. After he was murdered by Sean Donovan,Webb is no longer part of theSlow Horsesstory. As a result, a constant thorn in River and the team’s side has been removed. On the one hand, this would seem to be a positive, since Webb was a constant source of provocation. However, his absence simultaneously means that the show has lost one of its biggest sources of conflict and created the need for a new kind of enemy to emerge.

River Will Have A New Enemy In Slow Horses Season 4
James Webb Needs To Be Replaced
The fact that Webb is no longer on the scene creates a major hole inSlow Horses' story. On one level, he needs to be replaced, since the drama he provided was crucial to the show’s success and engaging character dynamics. However,finding a Webb surrogate is no easy task, since much of his appeal came from his history with River and the depth of their hostility – something that can’t be conjured inorganically.
…while this enemy will undoubtedly be a major concern for River, he won’t be able to replace the uniquely petty internal quarreling that made Webb such a deliciously hateable antagonist.
As theSlow Horsesseason 4 trailerand promotional material have already confirmed, Slough House will facea new threat in the form of Hugo Weaving’s Frank Harkness– a rogue CIA operative with a mysterious agenda. However, while this enemy will undoubtedly be a major concern for River, he won’t be able to replace the uniquely petty internal quarreling that made Webb such a deliciously hateable antagonist. The emphasis on a new and external threat may well help to pushSlow Horses' story forward, but it will be a marked shift from what has gone before – and proven so successful.
Slow Horses Needs To Establish A New Internal Threat
It’s A Key Part Of What Made The Show Successful
Even though finding a Webb surrogate is almost impossible given the uniqueness of the character’s relationship with River,Slow Horsesstill needs to find a way of replicating the low-level internal threat he represents. This is especially important now thatother MI5-based antagonists, like Duffy and Hobbs, have also been removed. Failure to do so will mean that the internal power-battles that have defined relationships inSlow Horses– from River’s infiltration of the Park, to Jackson’s duels with Taverner – will end up feeling slightly pedestrian.
Of course, the fact that characters like Webb, Duffy, and Hobbs were all killed in season 3 also presents a major opportunity for the show to reshape its version of MI5. Even though all three were reprehensible in their way, it could still be the case that whoever replaces them is even worse. The result could be a renewed rivalry between Slough House and the Park that, while not based on years of resentment, quickly becomes just as toxic. However, whatever approach the show takes, it’s essential thatSlow Horsesfigures out a way of replicating one of its core dynamics.