A quartet of space hippies on space-spanning motorcycles have been recruited to blow up the planet the Robinsons are living on in order to prove their worth to their government.
Meanwhile, the Robinsons are experiencing a bout of very strange weather. They try to prepare the Jupiter 2 for lift-off as soon as possible, but there are many systems that still need repair. Suddenly, a loud voice speaks to the Robinsons and orders them to leave the planet immediately as it is slated for destruction. The radar then detects visitors nearby, so Don and John go out to investigate.
Will, Dr. Smith and the Robot find a strange silver box that is very heavy. Although the Robot strongly urges him not to, Smith looks in the box and inhales a green gas that issues out of the box. Smith gasps and falls down, apparently dead.