Collision Course (1974)

arra, the enigmatic representative of a people whose giant planet is on a collision course with the moon, tries to convince the inhabitants of alpha that this meeting represents the last, definitive, evolutionary stage for their own people, as well as a possibility of life for the alphani themselves. carter first, and koenig then, are the intermediaries of this message but also the only ones to believe it, so much so that they are isolated from their companions when they decide to divert the lunar trajectory with targeted nuclear explosions. arra cannot allow it and the two alpha officers remain the only solution.