River Cartwright is ousted from MI5 and finds himself in a place worse than purgatory: Slough House, dumping ground for failed spies.

Taverner and the Slow Horses attempt different approaches to locate the kidnappers and Hassan. Ho makes a shocking discovery about Sid.

Jackson Lamb is on high alert after a former spy is found dead. Min and Louisa are tempted by an offer from outside Slough House.

Tearney makes a bold move. The Slow Horses assist the Tiger Team, unaware of their hidden agenda. Lamb and Ho take a road trip.

The Slow Horses fight for their lives. Lamb shares some devastating truths with Catherine.