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.