During preparations for a lunar probe launch, Colonel Steve Austin witnesses strange lights in the sky and becomes convinced it's a UFO. A family of four space explorers, each trained with specific tasks has crash landed on Earth, only to find that touching a human causes both parties great pain and will eventually kill the alien beings.

The HL-10, the vehicle Steve Austin was piloting when he had his crash two years ago, has been rebuilt and Steve is asked to have another go at it by his old friend Jay Rogers. Although Oscar Goldman is reluctant because the plane may have been sabotaged the first time around, Steve becomes obsessed with taking this second chance and seeing it through.