An asteroid is heading straight for Moonbase Alpha so the crew use Nuclear bomb to destroy the asteroid but Alan Carter (Nick Tate) one of the crew is to close to the explosion and is knocked out, and there is a radiation cloud surrounding Alpha which is stopping then finding eagle one on the scanners so Cmdr. John Koenig (Martin Landau) goes to find him is contacted by the voice of Arra (Margaret Leighton) directing him to Alan's location and in-doing so discovers that the moon is on a direct course with the planet Ithiria. The Crew of Alpha decide to use nuclear bombs to alter the course of the moon and planet but Cmdr. Koenig goes to the planet and meets Arra to discover that he, the moon and the planet have a destiny to meet and in doing so will allow the planet and all its inhabitant to evolve into a new spiritual life form but the crew are not willing to risk it and try to detonate the bombs but Alan and Koenig stop them just in time.
Review of Collision Course
