River Cartwright has been banished to Slough House and he greatly resents being one of the Slow Horses. When he learns of a young man being kidnapped and the snatchers are threatening to behead him, Cartwright sees a way out of exile but as he looks more and more into it, he finds that everyone remotely connected has his or her own motive and desires and none seem to be saving the lad nor getting Cartwright out of the House. Least of all Jackson Lamb.