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.

A London bombing puts Taverner under pressure. When River grows concerned for his grandfather, Louisa encourages him to go for a visit.

A naive agent makes a discovery about the Westacres bomber. Lamb suspects that David knows more than he's letting on.

River is trapped in France. Back at Slough House, the Dogs have come for Lamb.

Taverner is desperate to hide dangerous secrets. River seeks answers at his grandfather's house.

Lamb questions David about France as River comes face to face with the enemy.

Impossible decisions are faced and sacrifices are made.