Slow Horses Episode 4 'Lost and Found' Lands October 7 as the Frank Harkness Manhunt Tightens

Slough House is running out of time. Slow Horses Season 6 Episode 4, titled Lost and Found, premieres Wednesday, October 7 on Apple TV, and the episode promises to tighten the noose around the season's central mystery: who is Frank Harkness working for?

In the new episode, Jackson Lamb tries to figure out Harkness's employer while Sid, River, and Coe attempt to evade the hit squad on their trail — Kyle Soller's Jim and MyAnna Buring's Jane. It is classic Slow Horses: the spies are outgunned, outmaneuvered, and bickering the entire time, but somehow still the only people standing between disaster and the rest of us.

Where the season stands

Episode 3, Resurrection, which aired September 30, delivered two major developments: the return of Olivia Cooke's Sid Baker and the revelation that Moira Tregorian survived. The episode also introduced Lenny Rush as Reece Nesmith, adding another new face to the show's ever-expanding ensemble of misfits and manipulators.

The season is a hit by every available measure. Apple calls Slow Horses its No. 1 title in the UK, Season 6 is up roughly 25 percent versus Season 5 across its first seven days, and the show has re-entered Luminate's Top 50. It is also the show's biggest season yet in pure runtime: at around 50.3 minutes per episode on average, Season 6 is the longest so far, and the 60-minute finale — Judgment Day, airing October 21 — will be the longest episode in the show's history.

What makes this season's mystery so compelling is how personal it has become. Harkness is not just a target — he is a puzzle that reaches back into the history of the Service itself, and Lamb's investigation is peeling back layers that some very powerful people would prefer stayed buried. With the hit squad closing in and the finale titled Judgment Day, the show is clearly building toward a reckoning.

With just three episodes left after Lost and Found, the endgame is coming into focus. The manhunt for Harkness's backers, the hit squad closing in, and Lamb's increasingly desperate gambits all point toward a finale that the show's history suggests will be anything but clean. October 7 cannot come soon enough.