24 was one of Fox's most-watched shows in the early 2000's. Kiefer Sutherland starred as Jack Bauer, and anti-terrorist agent for the US. As the name of the show implies, the length of the season was drawn out so that the plot took place over 24 hours. Each hour-long episode gave viewers a real-time perspective of Jack's missions.
According to The Hollywood Reporter, Fox plans to bring Jack Bauer back to their television line up for a prequel series. The original series creators Joel Surnow and Bob Cochran are returning to helm the new show. The script is said to be on-going, unlike the close-ended limited shows 24: Legacy and 24: Live Another Day. It is unclear whether Kiefer Sutherland will reprise his role, and since there will be a significant age difference for the younger character it seems highly unlikely.
The last version of the show, called 24: Legacy, told a new story with Corey Hawkins (The Walking Dead, Straight Outta Compton) as the lead character. Although Legacy premiered after the Super Bowl last year and received massive ratings at first, viewership slowly dwindled down for the show by its finale. Fox canceled Legacy, and this new prequel series will be the future of the franchise.