We learn right away in Slow Horses season 3 episode 3 that the kidnapping of Standish (Saskia Reeves) was actually an inside job, ordered by Home Secretary Peter Judd (Samuel West) to test MI5's security system. As Ingrid Tearney (Sophie Okonedo) informs him, they failed, which Judd is extremely happy to hear, as not only is that going to allow him to bring in Chieftan as a private consultant to change MI5, but it puts him in the position of power with Tearney.
There's just one problem, Sean Donovan (Ṣọpẹ Dìrísù) isn't done with his mission yet. When he is supposed to hand Standish over to another Chieftan agent so she can be set free, Sean instead captures the agent and takes him as a hostage.
So, as Judd, and everyone else is going to learn, it is actually Sean who has the power in "Negotiating with Tigers."
The Grey Books
Marcus (Kadiff Kirwan) and Shirley (Aimee-Ffion Edward) are staking out Sean's apartment when Shirley has finally had it, deciding to break in and scope it out. Shortly after they get there, Lamb (Gary Oldman) calls them, explaining Standish being taken was a Tiger team operation, so they need to get back to Slough House. Shirley, however, decides to take a quick break to snort some cocaine, but is interrupted when Marcus discovers something major: the Tiger team operation was just phase one of Sean's plane, phase two is about the Grey Books, MI5's files on the world's biggest conspiracy theories. They give this info to Lamb, with Shirley believing Sean will keep Standish as leverage to get a look at the Grey Books.
Standish is also able to find out some key bits on her own. After being brought back to the safehouse, she is taken to the attic by the female member of Sean's team (Eliot Salt). Standish deduces that she and the other guy are siblings and this house is their family home; based on the height markers on a door frame that would make her Sarah or Allison (we know she is then Sarah).
Sean, meanwhile, takes a picture of the Chieftan agent with a gun to his head and sends it to the organization. They call back almost immediately, when he explains they won't get Standish or then agent back until his demands are met.
Lamb updates Taverner (Kristin Scott Thomas) on Standish still being held and Sean wanting the Grey Books. Standish is surprised she hasn't heard any of these demands, especially because the facility she supervises and visited in episode 1 is where the Grey Books are being held. For this tip, Lamb wants River (Jack Lowden) to be let go after breaking into the Park.
In custody
River is getting beat up by Duffy (Chris Reilly), pissed off that River played him. He tries to goad River to fight back, but River knows if he takes a swing at Duffy he'll be thrown out of the service, so instead he'll just take it, confident any second Lamb is going to get him out. Then there’s a knock on the door, but instead of River's ticket out it’s Hobbs (Chris Coghill), who wants to get a few licks of his own in after being embarrassed by River.
Shirley and Marcus have their own problems, as police were alerted about them breaking into Sean's house and come to arrest them. Marcu tells them they are MI5 and while they search for proof, the officer finds Shirley's drugs on her. Lamb is called by the police to confirm he gave them permission to search Sean's apartment and Shirley's drugs are part of a sting operation, he reluctantly says yes. The officer lets Marcus and Shirley go, even giving then drugs back, but Marcus grabs them before Shirley can and tells the officer to flush them. The officer has another message for them from Lamb: they're fired.
Finally, River is let out of the Park, but Duffy warns them to find the diamond or he's going to turn Slough House upside down. Away from then Park, after a backhanded compliment on River's actions, Lamb tells him Standish is still a hostage and tells him to meet up with Louisa (Rosalind Eleazar) at Chieftan to get what they can on Sean.
A spider in his own web
Ingrid returns to the Park and talks with Taverner, who tells her the Tiger team went rogue. This gives them an edge, wanting to let Chieftan clean up their own mess. They do recognize this situation could cause collateral damage, which would not bode well for Standish.
Lamb, meanwhile, meets with the head of Chieftan, Sly Monteith (Gavin Spokes). He tells him Standish and his agent are still being held in order to get a look at the Grey Books, which Lamb says people want because they think it'll prove some random conspiracies. But Sly knows nothing about this, so Lamb tells him to get it sorted.
At the Chieftan offices, Louisa and Guy bump into Spider (Freddie Fox), who says he didn't know that the operation wasn't real but now wants to be compensated for having gone through that. They are all let up to the main area where Spider actually reveals he is the one behind the operation, gloating how he played them. When Louisa tells him to give them the files as Standish is still a hostage, Spider blows it off, confident they have it under control. He also mentions he has a meeting with Judd about what they can do to improve MI5, which he says will include eliminating Slough House.
However, Spider is not as in control as he thinks he is (surprise, surprise). Sly arrives at the office and talks with Spider, upset about the situation and demanding an explanation. Spider is confident Sean won't do anything and plans to blow him off at a meeting he requested. But when Sly says Lamb mentioned the Grey Books, Spider is concerned how Lamb knew that. Sly demands Spider go to the meeting with Sean and get Standish and their agent back however he can.
So Spider plans to pay Sean off, assuming all he wants is more money. But Sean is adamant, he wants the Grey Books. Spider is tired of playing the game and tries to act tough against Sean, bringing up that he knows about his relationship with Allison. This angers Sean, who punches Spider hard enough that it appears to kill him, even though that was not Sean's intention.
Lamb shows up at a lunch that Sly and Judd are having, telling them until they get Standish back, he is going to be messing up whatever plans they have. As they talk, Sean drives by, blasting the car horn, quickly stopping, dropping Spider's body in front of the restaurant and then driving away. Seeing this, Lamb reminds Judd of the famous Winston Churchill quote, "you can't negotiate with a tiger when your head is in its mouth." When Judd's phone rings and it says it's from Webb, Lamb clarifies that it is the Tiger team, looking for his head.
New episodes of Slow Horses season 3 premiere Wednesdays on Apple TV Plus, where all previous episodes are also available.