London's Slough House is where the washed-up MI5 spies go to while away what's left of their careers. The "Slow Horses," as they're called, have all disgraced themselves in some way to get relegated here. Maybe they messed up an op badly, or got in the way of an ambitious colleague. Maybe they just got too dependent on the bottle—not unusual in this line of work. One thing these failed spies have in common, though, is they all want to be back in the action. Now the Slow Horses have a chance at redemption. An old Cold War–era spy is found dead on a bus outside Oxford, far from his usual haunts. As the agents dig in to their fallen comrade's circumstances, they uncover a shadowy tangle of ancient Cold War secrets. How many more people will have to die to keep those secrets buried?