AppleTV+’s spy thriller series Slow Horses brings another intense episode this week, as season 4 episode 4 deals with the still unclear situation regarding the London bombings while also possibly introducing a new theory. In the previous episode, we had found out that Frank Harkness was the main mastermind behind both the London bombings and the attempted assassination of the veteran MI5 officer David Cartwright. This time around, we are given a more concrete reason behind Frank’s plans and also his decision to send an assassin after David’s former bodyguard, Sam Chapman. Meanwhile, River finally returns from France, as he has more or less understood what went down at the Les Arbes house, only to find an even more surprising connection.

Spoiler Alert

Why did Frank Harkness plan the attacks?

While Frank Harness was earlier seen directly only once before, in season 2, episode 2, at the Les Arbes mansion where he had attacked River Cartwright,...