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

River and Sid join forces. A misfired gun has dire consequences.

Slough House is the unlikely venue for a secret romance, but events take a dark turn when a dangerous encounter becomes deadly.

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.

Lamb and Katinsky go head-to-head. Ho finds himself trapped on a train with a Russian assassin.

A romantic relationship in Istanbul ends badly. Lamb hits the panic button when one of his Slow Horses fails to show up for work.

River has to steal something out of the Park to save a life. Lamb realizes a stranger game is afoot.

Marcus and Shirley face Lamb's wrath. River discovers revenge is a dish best served cold.

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.

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

Impossible decisions are faced and sacrifices are made.