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 sends the Dogs to hunt down Lamb and the Slow Horses. River holds the secret to saving the gang.

The Slow Horses must disappear to avoid capture by MI5. Lamb and River head to The Park to outwit Taverner.

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 liaises with a Russian defector who may hold a clue to sleeper agents. River is on the trail of a ruthless assassin.

River gets cozy in the Cotswolds while searching for a sleeper agent. Min discovers Russian drinking games are the most brutal of all.

Louisa makes her move on Pashkin. Catherine makes moves of a different kind when she plays high-stakes chess with a sinister stranger.

Lamb orders his Slow Horses to walk into traps. River believes something alarming is heading toward London.

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.

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

Taverner and Tearney face off for control of MI5. River and Louisa find themselves caught in the crossfire.

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.

A mass shooting rocks London, intensifying a testy mayoral race. Shirley believes one of the Slow Horses was the target of an attempted hit.

Lamb intercepts an assassin. Taverner receives a key piece of intel about the Abbotsfield shooting.

An act of sabotage grinds London to a halt. Taverner interrogates Roddy. Coe is convinced a destabilization strategy is at play.

Flyte sets out to find Roddy's girlfriend. The gang is dispatched to two different campaign events to prevent another attack.

Lamb debriefs River and Coe. Roddy is pulled in to help decipher a piece of code as the destabilization strategy nears its final stage.

It's up to the Slow Horses to stop Farouk's team from completing its mission in a final act of mass carnage.