The fourth season of the thriller series Slow Horses will be released on Apple TV on September 4, 2024. In the series, we follow secret agents Jackson Lamb (Gary Oldman) and River Cartwright (Jack Lowden) as they work for the British secret service MI5. Cartwright was transferred to Lamb’s unit as a punishment after making an embarrassing mistake and wants to make amends for his failure. In season 4, Hugo Weaving appears for the first time as antagonist Frank Harkness.