London’s Slough House is for washed-up MI5 spies with failed careers. The “slow horses,” as they’re called, have all disgraced themselves in some way to be relegated there. Maybe they botched an Op so badly that they can’t be trusted anymore, or maybe they got too dependent on the bottle. They all have one thing in common: they want back in the action. And most of them would do anything to get there─even if it means working together.

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?