A romantic liaison in Istanbul threatens to expose a buried MI5 secret in London. When Jackson Lamb and his team of misfits are dragged into the fight, they find themselves caught in a conspiracy that threatens the future not just of Slough House but of MI5 itself.

A whole year on from the last time we met them, and Lance is still lovelorn after the departure of his ex-wife. But just maybe he is about to surprise everybody with a new relationship. Meanwhile, Andy and his wife Becky are now proud parents, facing all the responsibilities that brings, but despite qualifying as an archaeologist Andy is still mostly unemployed and their shared hopes for the future look further off than ever.

In season 4, a bombing detonates personal secrets, rocking Slough House's already unstable foundations.

This series follows the lives of sixth form students Tony Stonem, Michelle Richardson, Sid Jenkins, Cassie Ainsworth, Chris Miles, Jal Fazer, Maxxie Oliver, Anwar Kharral and new character Lucy "Sketch".

In season five, everyone is suspicious when resident tech nerd Roddy Ho has a glamorous new girlfriend. When a series of increasingly bizarre events occur across the city, it falls to the Slow Horses to work out how everything is connected. After all, Lamb knows that in the world of espionage, the London Rules — cover your back — always apply.

Six strangers are brought together by a divorce support group who quickly transform from therapy-seeking victims into architects of retribution. With little in common beyond their pain, they form an unlikely bond. What begins as a cathartic outlet quickly spirals into something far more dangerous.