sha Donovan and Allison Dunn two British Spooks stationed in Istanbul are caught in a spy versus spy drama Donovan's got a hunch that Allison might be pocketing a top secret file so he Trails her of course in classic Chase fashion he loses her in the chaos Allison then does a sneaky swap of the file with a shadowy figure only for Donovan to later discover she's been murdered fast forward a year to slow house where the team is stuck in their usual boring tasks Katherine stish is at an AA meeting when Donovan Dawning a disguise as a fellow attendee slides into chat they go to a cafe but Catherine starts to get the heebie jeebies and tries to bail too late Donovan's crew swoops in and snatches her the next day the slow horses are scratching their heads over Catherine's Vanishing act Shirley and Marcus raid her apartment Louisa digs into her last whereabouts and River cartright gets a chilling photo of Catherine with a gun to her head and a message barbin Bridge one minute or she's toast he Zips over to barbin bridge expecting a bit of drama instead he finds James spiderweb looking nervous and jittery someone kidnapped her sister too and want prime minister vetting file from MI5 headquarters and just when River's about to brush it off as a bad joke he spots a snipers laser dot dancing on web's forehead River decides its go time and sneaks into MI5 HQ under the guise of having found a missing Diamond he manages to snag a security pass and slinks his way to the records department like a pro meanwhile back at slow house Louise is connecting the dots between an abandoned car and Donovan Lambs realizes they're being watched and dander and Longridge are having a tough time tailing one of the mysterious Watchers lamb finally pieces it together the kidnappers are actually a tiger team hired by MI5 to run a security test he Rings up River letting him know that Catherine life isn't actually on the line River successfully make his Escape but of course gets caught by the ever watchful security River gets a payback from Duffy for making him look like an amateur meanwhile lamb uncovers a juicy tidbit standish's kidnappers are actually from Chieftain a private security firm hired by Home Secretary Peter Jud Jud just wants to strong arm Tierney in privatizing MI5 security giving business to his friends Chieftain but things take a wild turn when Donovan who's supposed to be working for Chieftain decides to go Rogue he snatches both sish and a fellow Chief and operative dander and Longridge dig into Donovan's scheme and discover he's after mi5's gray books the ones with all the juicy conspiracy theories lamb manages to get River out of his tight spot and sends him and guy to chieftain's HQ there they find out that Webb was in on the whole plot when Webb tries to negotiate with Donovan it ends in a a tragic mixup and web accidentally meets his end lamb takes the fight straight to Jud at a Swanky restaurant only to find Donovan dropping web's body at the same spot tuni plans to allow Donovan access to the gray books in return for standish's release and then have him arrested by Duffy but Donovan teaming up with Allison dun's siblings has a Twist up his sleeve he's on a mission for justice for Allison's death sish moved by The Plea helps them out by pointing them to the file they really need meanwhile ho tracks down the safe house and he and lamb set off to rescue stish River and Guy escort Donovan and Ben to the file storage facility only for Ben to drop a bombshell the gray books were a red herring he's actually after a different file entirely Tierney soon figures out that someone inside MI5 has hidden a file in the facility Duffy is ordered by tyranny to kill everyone inside the facility to ensure the file isn't leaked Tierney faces off with tavner she knew tavner was Donovan's mole and had planted the footprint file which holds explosive evidence of TI's dirty laundry that could spell her undoing Allison was set to blow whistle on her butt she got her killed as Chieftain operatives gear up to raid the file storage facility River sends out a distress call to lamb and requests backup from slow house dander and Longridge eager to get their jobs back arm themselves and head to the scene meanwhile Chieftain agents don't waste any time they capture and execute the facility security guard lamb manages to rescue stish from sahun at the safe house but they get ambushed by Sturges and Hobs at the facility river guy Ben and Donovan are fighting off the chief in assault amid the chaos they manag to locate the footprint file but Ben doesn't make it out alive lamb rigs the dun house with booby traps and when Hobs and Sturges show up there in for a nasty surprise ho tries to assist by crashing a bus into the house but he arrives just a smidge too late to be of any real help at the file storage facility Donovan makes the ultimate sacrifice buying enough time for River and guy to grab the footprint file and Escape dander swoops in to rescue them from Duffy's Ambush while Longridge takes Duffy on in a brutal fist fight guy finishes the job by Smashing Duffy with a rock just to be sure later lamb drops bombshell on sish her supposed hero Charles partner was actually a double crossing traitor using her for his own ends devastated stish decides to resign from SLO house River meanwhile takes the footprint file to his grandfather who destroys it to protect mi5's reputation but River one step ahead he's already made a copy and leaks it out the Fallout is immediate tyy and jut are ousted and Taver steps up to take over his first death ask