When the Enterprise-D rescues a scientist from apparent destruction by a mysterious energy wave, his reaction is odd enough to cause Picard to consult with Guinan. She informs him of a time when she encountered a similar energy wave, and how its alluring properties now make this scientist a powerful threat to the crew and anyone standing in his way. Further investigation reveals that the scientist is indeed intent on returning to the wave, even if it means destroying whole worlds to affect gravity in such a way as to bring the wave to him. When Picard enters the wave, the Nexus, he finds out why it's so alluring—and an unexpected means of defeating the scientist's plan. Inside the Nexus is an idyllic life for all who enter—and one of those who entered some time ago was the legendary James T. Kirk. Long presumed to have died saving the Enterprise-B, it's now apparent to Picard that, in fact, Captain Kirk had merely "crossed over" into the Nexus. Kirk knows there's something slightly false about this "perfect retirement" he's been enjoying, but it takes Picard to convince him that it's actually masking a dangerous threat to the "real world". Kirk is somewhat reluctantly drawn out of the Nexus by Picard, and together they stop the scientist's world-destroying plan. Billions of the Federation's citizens are saved, but at the cost of the life of one of the two famous Enterprise captains.