Apple TV+'s spy thriller Slow Horses has killed off several of its most prominent characters over three seasons, making it understandably difficult to track who has died and how they met their end. Although the central Slough House team has remained largely consistent, every season introduces significant new players, only for many of them to meet an unfortunate end by the story's conclusion. As a result, following the major character deaths is an easy way to understand how the show's wider narrative has developed ahead of Slow Horses season 4.