London, England: Slough House is where washed-up MI5 spies go to while away what's left of their failed careers. The "slow horses," as they're called, have all disgraced themselves in some way to get relegated there. Maybe they botched an Op so badly they can't be trusted anymore. Maybe they got in the way of an ambitious colleague and had the rug yanked out from under them. Maybe they just got too dependent on the bottle--not unusual in this line of work. One thing they have in common, though, is they want to be back in the action. And most of them would do anything to get there─even if it means having to collaborate with one another.

When a young man is abducted and his kidnappers threaten to broadcast his beheading live on the Internet, the slow horses see an opportunity to redeem themselves. But is the victim really who he appears to be?