The cruiser Peleliu is sent to take Enterprise’s place guarding Belle Terre, but its captain, Roger Lake, is acting irrationally due to a previous exposure to an alien methane gas. With Peleliu nearly destroyed and a lot of its crew killed in an ambush by the Kauld, the acting second-in-command, Nick Keller, takes control of the ship. The ambush had been planned by Billy Maidenshore, who had escaped from imprisonment on Belle Terre and had taken over the mining vessel Pandora’s Box, and was also holding McCoy and Uhura captive. Uhura later disables Maidenshore’s ship, and they are rescued. Kirk had taken the Enterprise to try to locate where the robots, that had started collecting the olivium and putting it back in the quake moon, were coming from. Scotty was still helping out on Belle Terre, and Keller talks him into helping put together a workable warship, out of the remains of Peleliu and some of the components from the ships that had brought the colonists to Belle Terre. On the first test flight they get word that a fleet of Kauld ships are approached, and they intercept them, only to have the Kauld immediately surrender to them, asking for help in saving their planet from an energy eating entity that is heading towards them (apparently attracted by the olivium they have been siphoning off from Maidenshore’s horde). Meanwhile Kirk and the Enterprise have made the entities behind the robots reveal themselves, through the captain of a survey vessel, Mitch Dogan, who was believed to have died in an accident related to the quake moon, but who had been saved by these transdimensional beings. These beings are planning on collecting their olivium and moving on, and the energy-eating entity was originally theirs, but got “lost”, and the beings had lost the ability to locate it. They give the Enterprise the ability to move in their realm, and Kirk is able to trap the entity just before the Challenger (which is what Keller had named his new vessel) attempted a probably futile attack on it. The help offered by the Challenger causes the Kauld to reconsider their previous attitude to other species, and the Enterprise leaves the area with the region considerably more secure.