Imagine being confronted by an extraterrestrial: "You are soon to be engulfed in an impenetrable shroud which will stifle your seed and petrify your being. To perpetuate your kind, you must venture into the unknown." What would you do? What could you do?

An immense spacecraft enters Earth orbit and gobbles up a Space Shuttle and nuclear missiles sent to destroy it. A humanoid alien, Theo, meets with world leaders and offers to assist in designing a spaceship-building program and in preparing young earthlings to become nomads of the universe.

When Theo terminates his purification program, undertaken to eliminate from the exiting specimens the destructive forces cemented in the native species, he is persuaded to allow tens of thousands of young couples to remain on his craft, to increase the chances of survival of the human species. Only after the alien ship reaches deep space will these volunteers discover Theo's sinister reason for his visitation.

Meshed within the drama is the budding relationship between Professor David Gannett, who was aboard the captured Shuttle, and Cora Martin, a virtuous young woman who resists temptation, succumbs to her baser instincts, and is finally sanctified within the alien vessel.