An alien named Altovar approaches Bashir to obtain a restricted substance. The doctor refuses, prompting Altovar to later break into the Infirmary. Bashir arrives and tries to stop him, but the alien renders him unconscious with an electrical discharge. When Bashir recovers, he finds the temples of his hair graying, and the station dark and deserted. Just the most vital systems still function, and although he periodically hears strange whispering sounds, the only inhabitants found are Garak and a terrified Quark. Bashir and Garak split up in hopes of learning the fate of the others. Suddenly, his path is blocked by a forcefield, and he senses a presence coming toward him.
Thinking quickly, Bashir ducks inside a turbolift and narrowly escapes the pursuing Altovar. He exits to find Kira, O'Brien, Odo, and Dax engaged in a heated discussion. Bashir now appears to have aged 25 years, but the group is too busy debating each other to notice. The doctor realizes that the whispering, the crew's strange behavior, and the technical problems must be connected. O'Brien fixes the communications relay, and the group hears the same whispers. As the sounds become clearer, they prove to be the distant voices of the crew, stating that Bashir is in a telepathically-induced coma and will be dead in less than three hours. The doctor scans himself and discovers that he is indeed in a coma.
Bashir realizes that the rest of the group really isn't there — this scenario is actually happening in his mind, which is represented by the station, and the others just embody different aspects of his personality — fixing the station will bring Bashir out of his coma. Unfortunately, Dax is captured by the alien, and Bashir suddenly finds himself with Garak, who directs the doctor to Ops in order to repair the damage. On his way, Bashir sees Sisko, who represents the best aspects of the doctor's personality. But Altovar captures Sisko, then tells Bashir he will kill each part of his personality before finally letting him die.
While trying to get to Ops, Bashir, who appears about 75 now, finds Kira dead and Odo dying. He and O'Brien end up at Quark's, where the crowd is betting on how and when Bashir will die. Altovar appears, killing Quark, and Bashir starts to run away, but is terrified to discover he has broken his hip.
Bashir, now about 100 years old, is helped to Ops by Garak, who keeps encouraging him to give up. Bashir then realizes that Garak is actually Altovar. At this point the alien reveals his true form, but Bashir, having recovered some of his confidence, gains the upper hand. He returns to the Infirmary, realizing that this is the center of his world — and, therefore, the place from which he should repair the damage. Immediately, he is able to restore the lights, trap Altovar in a forcefield, and disintegrate the alien. He then quickly regains consciousness, surrounded by his crewmates, who he prepares to tell of his bizarre experience.