Space:1999 Another Time, Another place

In this episode, a distortion in time creates two separate moons, each with its own Alpha crew from different eras. The Alphans discover that the moon is returning to Earth's solar system, but Regina Kesslann mysteriously dies when the moon re-enters Earth's orbit. They are unable to contact anyone on Earth, which seems to have experienced an extinction event. Suddenly, another moon appears in Earth's orbit, on a collision course with their own. A reconnaissance mission is assembled to find answers.