They draw lots, and physicist Dr. Allen Leighton is chosen to undergo radical surgical procedures that will transform him into an inhabitant from the planet Theta.
His wife, Yvette, persists in not believing he is dead; she even feels sympathetic pain as Allen suffers on the operating table.
Complications arise when the effects of Leighton's transformation extend beyond his physical appearance and begin to affect his mind, a situation compounded by the scientist's strong emotional connection with his now-pregnant wife.
The scientists' plan is for Leighton, as the Thetan creature equipped with an energy weapon and spaceship, to land at the United Nations in an effort to create initial panic.
Leighton, now a perfect simulation of an inhabitant of the planet Theta, is launched into orbit as a weather satellite, but the mission goes awry when the spaceship comes down off course and lands in a wooded area near the United Labs facility.
After disintegrating their station wagon with his laser pistol, Allen is severely wounded by three armed hunters as he emerges from the underbrush.
A lesson, at last, to be learned.The prosthetic suit for the monstrously altered Allen Leighton was judged by some of ABC's local affiliates to be so frightening that they broadcast a black screen during the Thetan's appearances, effectively censoring most of the show's last act.