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 destabilisation strategy is at play.

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.