Slough House is a dumping ground for British intelligence agents who've screwed up a case - say by leaving a secret file on a train, or blowing a surveillance. River Carter, one such "slow horse," is bitter about his failure and about his tedious assignment transcribing cell phone conversations. When a young man is abducted and his kidnappers threaten to broadcast his beheading live on the Internet, River sees an opportunity to redeem himself. But is the victim who he first appears to be? And what is the kidnapper's connection with a disgraced journalist? As the clock ticks on the execution, River find that everyone has his own agenda.