Syfy is doubling down with “Childhood’s End” and “The Expanse,” setting the projects to premiere back-to-back on Dec. 14.

“Childhood’s End” is a six-hour event series based on Arthur C. Clarke’s sci-fi novel and deals with what happens after alien Overlords take over and promise to eliminate poverty, war and sickness — but what do they ultimately want from Earth? It has a cast that includes Charles Dance, Mike Vogel, Daisy Betts, Yael Stone, Julian McMahon, Osy Ikhile and Colm Meaney.

It’s written and adapted by Matthew Graham, who exec produces along with Akiva Goldsman. Alissa Phillips is co-executive producer. It’s directed by Nick Hurran. The Universal Cable Productions series will air from 8 to 10 p.m. on Dec. 14, 15 and 16.

“The Expanse,” which is based on Daniel Abraham and Ty Franck’s bestselling book series of the same name, is set 200 years in the future and explains that mankind has since colonized the solar system. It’s also a mystery series and follows a hardened detective (Thomas Jane) and a rogue ship’s captain (Steven Strait) who come together to find a missing young woman and end up in a race across the solar system to expose the greatest conspiracy in human history. The first two episodes, which are directed by Terry McDonough, will premiere at 10 p.m. Dec. 14 and Dec. 15, respectively. The rest of the 10-part first season will air at its normal time of 10 p.m. Tuesdays.

Mark Fergus and Hawk Ostby wrote the pilot of “The Expanse” and serve as writers and executive producers. They also serve as showrunners with fellow executive producer Naren Shankar. Sean Daniel and Jason Brown of the Sean Daniel Company, who developed the original pitch as a direct-to-series project with Fergus and Ostby, are also exec producing. Ben Cook serves as a producer. Abraham and Franck are also producing.

“The Expanse” is financed and produced by Alcon Television Group (ATG), which is a division of Alcon Entertainment. Alcon co-founders and co-CEOs Andrew Kosove and Broderick Johnson are executive producing along with former Alcon Television president Sharon Hall. Alcon Television executive Ben Roberts serves as co-producer.