'Slow Horses' Full Recap (Seasons 1-5) To Prepare You For Season 6

Ever since AppleTV brought Mick Herron’s spy thriller books to the screen through Slow Horses, it has turned into one of the most successful and beloved shows on the streaming platform. Helmed by brilliant actors like Gary Oldman, Kristin Scott Thomas, and Jack Lowden, and driven by truly entertaining plotlines every season, the series has been equally loved by fans and appreciated by critics. At the center of it is the Slough House, an ill-reputed department of the MI5 where agents who have failed terribly at some mission are sent or demoted to. Considered a banishment room and a hell-hole for MI5 agents, the Slough House employees, often called the Slow Horses, are supposed to complete menial paperwork and do the dirty work for their superiors, and are intentionally kept away from serious investigations. Before the release of the much-anticipated Slow Horses season 6, here’s a detailed recap of everything that has happened in the series so far. 

Spoiler Alert

Slow Horses season 1 introduced us to River Cartwright, who was demoted to the Slough House after a botched live training exercise. After making acquaintances with the grumpy, unethical, and rather gassy boss, Jackson Lamb, and the other disgraced agents who had been demoted to the department just like him, he and the team were assigned the duty of keeping an eye on Robert Hobden, a journalist known for his affinity for right-wing ideology. Hobden claimed to have insider information about some serious violent attack about to take place in London, and within a couple of days, the authorities were alerted to a horrific development. A right-wing nationalist group called the Sons of Albion had kidnapped a young student named Hassan Ahmed, and openly threatened to behead him on a livestream, to send a clear message to Muslims and other immigrants living in the country.

When Lamb and River reached the house where Hassan was supposedly being kept hostage, they found the beheaded corpse of one of the kidnappers, Moe. This was when the real truth of the matter was revealed: the MI5 heads knew that the kidnapping would happen, and they had allowed it to happen because of diplomatic reasons. Hassan Ahmed was the nephew of an important Pakistani diplomat, and his British counterparts wanted to make it seem like they had successfully rescued his nephew in order to improve the diplomatic relations between the two countries. Therefore, MI5 knew about the plan, and the deputy director, Diana Taverner, allowed the kidnapping to go through, and she had placed an undercover agent, Alan Black, among the Sons of Albion to ensure that the situation would not get out of hand. But things did get out of control when the other kidnappers suspected Alan Black, codenamed Moe, of being a snitch, and murdered him to then disappear with their hostage. In the recent past, River had photographed Diana and Alan while on a surveillance training mission to follow the Second Desk, and this was why Diana had intentionally had his live training mission jeopardized. Her intention was to ensure that River would never be able to tell anyone about what he had unknowingly witnessed, and since firing him directly would have raised alarms, she had gotten him demoted to Slough House instead.

Despite MI5’s agenda behind the kidnapping, the Sons of Albion group were dead serious and genuinely wanted to kill their hostage. The journalist Robert Hobden had overheard a conversation that made him realize what the MI5 was up to, and he wanted to expose it through other journalists. At one point, he tried approaching an MP, Peter Judd, with the information he had, but unfortunately for him, the politician made a deal with Diana Taverner and had Robert Hobden killed. Hassan Ahmed was ultimately saved, but the situation led to Diana and Judd making a deal, which would continue throughout the next seasons. Meanwhile, it also resulted in Diana Taverner and Jackson Lamb becoming enemies who also had to rely on each other for the sake of their teams. 

The stakes were raised higher in the 2nd season of Slow Horses, adapted from Mick Herron’s novel Dead Lions. The season began with the mysterious death of Dickie Bough, an ex-MI5 agent who had been murdered after he had left a single message on his phone—Cicada. As it happened, cicada was the codeword used to refer to KGB sleeper cell agents who had been placed in British society during the Cold War. Fearing the worst, Jackson Lamb got in touch with an old acquaintance named Nikolai Katinsky, who was once a KGB spy before being fired and seeking asylum in England. Katinsky confirmed that the cicadas were very real, as he had himself once seen their leader, Alexander Popov. From the security cameras, it was clear that Dickie Bough had been murdered by a Russian hitman named Andrei Chernitsky, who also seemed to have flown out of England from a flying club in the village of Upshott.

Investigating this flying club was the next course of action, and River stood up to the task, by taking on the false identity of a journalist. In Upshott, he did not only find Chernitsky, but also realized that he was in close contact with Alex Tropper, an old KGB agent who had been living as a cicada for so long. River also found out that Alex had just flown her private plane from Upshott, carrying explosives and headed to London, to carry out a terrorist attack in the vicinity of the Glasshouse hotel. But ultimately, a much grander scheme was revealed by the end of the season, as the Russians were very much involved in foul play on British soil, through the modern version of the KGB, the FSB. The Russian authorities wanted to silence an oligarch named Ilya Nevsky, who had been living in London for several years, and had been extremely critical of the Russian government. They wanted to retaliate by having Nevsky killed and all his funds transferred back to the country. While they managed to have Nevsky killed by a mercenary they had hired, Arkady Pashkin, and also had the oligarch’s thumb cut off, they still needed to access Nevsky’s office to transfer the funds. 

The office was situated inside the Glasshouse hotel, for which the building had to be cleared, and so they had used the cicadas to create a false alarm to have the entire building evacuated. After River was convinced that a plane full of bombs was being flown to London for an attack, he also found out that this was not the case, but rather a decoy plan. But since he had already alerted MI5 about the situation and the area had been cleared, the Russians got to access Nevsky’s office and transfer the funds. Their mercenary, Arkady Pashkin, tried to betray them and get away with the oligarch’s diamonds, but was ultimately shot dead by the new Slough House agent, Marcus Longridge. The Slow Horses managed to solve a difficult case once again, but had lost one of their own this time, as Min Harper was killed by the Russians after he learned too much about the conspiracy.

The 3rd season saw the coming of a new faction called the Tigers, who had apparently gone rogue, as they decided to kidnap Slough House agent Catherine Standish and ask for access to a particular file from the MI5 archives as ransom. But just like every other time, things were not as simple as they seemed, as the Tigers turned out to be ex-MI5 agents hired by MI5 Second Desk Diana Taverner herself, who wanted to sabotage the position of her boss, Director-General Ingrid Tearney. Diana wanted to expose the terrible secrets of Tearney and replace her as the new head of MI5, for which she took the help of her old fiendish friend, Peter Judd, who had climbed up the ranks of politics with her support. Judd had appointed the private security firm Chieftain, owned by a close friend of his, to have Catherine kidnapped and handed over to the Tigers, and River was encouraged to break into the Regent’s Park headquarters of the agency in search of a file about the Tigers.

Judd’s (and Diana’s) intention was to use these incidents as proof of the failing efficiency of MI5 and blame the Director-General. Hatching a plan against Ingrid Tearney was not a tough task either, as the First Desk had given the order to use surveillance against enemies who had caused significant harm to innocent civilians. When an agent named Alison Dunn had tried to get hold of a file that proved what Taverner had done, the latter had Alison killed. Therefore, the slain agent’s aggrieved lover, Sean Donovan, who was also an MI5 agent, readily agreed to work for Diana at present, after he was promised access to the file over which Alison had been killed. Meanwhile, Tearney threw all caution to the wind after she realized that her second-in-command was trying to expose her with the help of the Slough House agents, and she ordered the Dogs tactical unit as well as the Chieftain group, who were now under her command, to protect the file at any cost. However, things ultimately turned in the Second Desk’s favor, as River managed to retrieve the file safely and expose all the details in it, which immediately took down Tearney and made Diana Taverner the ideal candidate to be the new Director-General of MI5. However, instead of taking the position herself, Diana eventually handed it over to Claude Whelan, a man she could easily control from the shadows and yet pin the blame on if anything ever went wrong.

The fourth installment made matters even more personal, opening with a deadly bomb blast in the heart of London. Just two hours later, an intruder tried to kill the aging ex-MI5 Director, David Cartwright, by pretending to be his grandson, River. Things took an even weirder turn when the IDs found on the perpetrators revealed that they were MI5 cold bodies, meaning fake characters invented to carry out certain off-the-book operations. In order to solve the case that was so dear to his heart, River travelled to France in search of more clues, and this is where he ultimately learned a shocking truth. Many years back, David Cartwright’s only daughter, Isobel, had run away from her home to go live with a mercenary named Frank Harkness in France, whom she must have believed to be a revolutionary with noble intentions. However, Frank was a criminal, whose only dream was to create his own kill squad with his own biological sons as members.

When Isobel soon fell in love with Frank, he took advantage of the situation, knowing very well that she was the daughter of the MI5 Director. Thus, he negotiated a deal with Frank, according to which he would let Isobel leave, in exchange for multiple fake IDs made and supported by the MI5, or cold bodies, with which he could accept and execute global private missions with his kill squad. Although Isobel was returned, she was crucially pregnant with Frank Harkness’ child, who was named River Cartwright after he was born. All of this would have remained hidden unless one of Frank’s sons messed up a contract that his kill squad had taken in the recent past. 

Instead of killing the intended target, the terrorist blew up the bombs at a shopping center, killing innocent victims, before posting a rant video online about how he had taken action against the cruel powers that be. As a result, Frank had to do something to ensure that his involvement with the bombings, and with MI5 in the past, would remain a mystery. Only two men had known about the secret deal he had made with MI5 in the past: David Cartwright, and his trusted friend, Sam Chapman. Therefore, Frank had ordered hits on both these men, but since David managed to survive, his estranged son, River, started investigating the case and led to Frank’s real identity getting revealed. Nonetheless, Frank Harkness was ultimately allowed to walk free, as he threatened to expose to the world how MI5 itself had hired his kill squad on numerous occasions to get rid of targets who could not be dealt with legally. Despite wanting to have no connection with his biological father, River had to tolerate Frank making a promise to return to his life. Meanwhile, another significant member of the Slough House had fallen, as Marcus Longridge had been killed.

Last year’s iteration of Slow Horses began with the most preposterous and unbelievable of situations, as the egoistic big-mouth hacker of the Slough House, Roddy Ho, managed to get a girlfriend, named Tara Younis. Despite everyone else finding the situation absolutely ridiculous, Roddy was confident that he had genuinely gotten a girlfriend who wanted to spend the rest of her life with him. Turned out, Tara was actually a member, and at times leader, of a group of Libyan militants who wanted to seek revenge against the British, who had colonized their country and looted all their wealth and resources. Getting close to the tech expert, Tara had essentially made her way into the MI5 computer network and frozen it until her group was paid 100 million pounds in compensation for what the colonialists had done to her homeland. 

The group had thought out the plan really well, as they hired the ex-Home Secretary, Peter Judd, who had turned into a private contractor after retiring from politics. They used Judd’s personal relations with figures of authority to plan their motives further. The group ended up following the British government’s destabilization policy, which involved attacking a nation in various ways until they fully surrendered. Similarly, Tara and her group had started with carrying out a terrorist attack in which 11 innocent civilians had been killed, and they eventually threatened to carry out the last step as well, which was to attack a place of worship. With millions of citizens having gathered in churches for Sunday mass, this was a threat that needed to be dealt with seriously. 

Although the ransom money was initially paid to Tara, she was eventually arrested by Jackson Lamb, while her other three associates refused to put down their arms and instead attacked a multi-faith center. Two of them had to be shot dead by Slough House agents, while a third one tried to kill MI5 Director Claude Whelan. Despite being saved by the Slow Horses, Whelan continued to try and dismantle the Slough House department altogether, as he considered them to be an unnecessary financial burden on the agency. Therefore, Jackson Lamb had to use his ultimate weapon: a recording which proved that Claude Whelan had a terribly ill habit of hiring escorts on a daily basis, and when a politician and his columnist wife tried to expose him, he threatened them with their lives. Thus, it was Whelan who was forced to step away from the service, while the Slough House survived to live another day, and Diana Taverner finally became the Director General of MI5.