Staite is best known for her work on TV's "Firefly." Buckley co-starred on "Supernatural."
Their science-fiction collaboration "Doomsday Prophecy" is to air Aug. 13.
"A book editor [played by Buckley] and an archeologist [played by Staite] hunt down a mysterious author of prophetic novels," Syfy said in a synopsis. "When the writer is found dead, the editor obtains a device enabling him to see the future -- an impending geological nightmare that will tear apart the planet."