Olivia Cooke on Returning to ‘Slow Horses,’ On-Set Injuries and That Shocking Finale Cliffhanger: ‘I Want a Showdown!’

SPOILER ALERT: The following article contains plot details from “Judgement Day,” the Season 6 finale of “Slow Horses,” now streaming on Apple TV. “Hello, River.” Those two fateful words announced Olivia Cooke’s return to “Slow Horses” after a four-season absence from the Apple TV spy drama.