Apocalypse decides a super-soldier would make one fine horseman for him. Steve thinks he can save the world on his own by destroying Apocalypse from the inside his cult. Bucky disagrees on both accounts and sets off to save Steve.

+ Bucky helps to shake off Steve's brainwashing
+ or both Bucky AND Steve end up as horsemen
+ Apocalypse is confused by their skills, since he can't absorb them like mutant abilities