Kirk, Spock, McCoy and a couple of red shirts beam down to the surface of a planet in answer to a fake distress call. There they are overpowered by a small group of human-looking aliens from the Andromeda galaxy, led by Rojan. Their galaxy will be uninhabitable within a few thousand years, so they intend to conquer ours, to give themselves a new home. The aliens' spacecraft had been damaged by the energy barrier around the galaxy, and they need the Enterprise to return home, enhancing its engines so that the journey will “only“ take 300 years. They take over the Enterprise using their two main weapons - a paralyzing beam, and a ray that can reduce a person to a gray block of material - revival only being possible if the block is not damaged. After successfully negotiating the energy barrier, the aliens reduce all the crew into the gray blocks, with the exception of Kirk, Spock, McCoy and Scott, who must somehow overcome the aliens, revive the crew and return home.