Bashir awakens to find the computer offline and the station in shambles. He makes his way to the now dark and deserted Promenade. As he investigates the situation, he sees himself reflected in a control panel and notices what seems to be a bit of grey in his hair. Arriving in Quark’s, he finds the Ferengi hiding behind the bar. Before Quark can answer any questions, a shadowy figure approaches, prompting him to flee. Bashir follows suit, eventually reaching the security office, where he is surprised to encounter Garak.
The situation is grim, as the station’s systems are offline, save for life support and an assortment of basic functions, and there is an unknown and extremely dangerous intruder aboard. When Bashir hears distant, indistinct voices, Garak is puzzled (he hears nothing) and remarks on how grey Bashir’s hair is getting. Each man takes a phaser before splitting up. While walking down a corridor, Bashir hears something behind him and finds himself trapped behind a forcefield as the lights begin to shut down.
Bashir ducks into a turbo lift, narrowly escaping the intruder, who he now recognizes as the Lethean. After leaving the turbo lift, he enters the wardroom where he is relieved to find Odo, Dax, O’Brien, and Kira alive and well, though none of them is quite acting like themselves. Odo is paranoid, Dax is trigger-happy, O’Brien is cowering, and Kira is just angry (well, moreso than usual). After some bickering, the team agrees to head for a cargo bay, where O’Brien thinks he can access what he needs to get the station up and running. Once there, O’Brien gets to work while Kira, Odo, and Dax continue to bicker. Bashir is convinced that there’s something wrong with his friends, though Kira is quick to remind him that between the voices he’s been hearing and the fact that he now looks about sixty years old, he’s hardly one to throw stones.
O’Brien interrupts when he picks up a strange audio signal. It appears to be Dax, saying that Bashir is comatose and mere hours from death. A quick tricorder scan suggests that the voices know what they’re talking about.
Bashir turns his tricorder on the others, picking up no life signs from any of them. He soon realizes that this is all in his head, that the station is his mind while the others represent different aspects of his personality and the Lethean is whatever it is that’s killing him.
Suddenly, that self-same Lethean appears and makes off with Dax. Just as suddenly, Bashir finds himself playing tennis with Garak. Still aging, Bashir begins to make his way toward Ops. As he does so, he passes through a corridor full of wounded crewmen, who are being tended to by none other than Sisko, representing Bashir’s professionalism. True to form, though, no sooner does the commander agree to help Bashir than the Lethean appears, pulling him into a wall. Bashir runs, only for the Lethean to appear once again. He’s here to gloat, telling the doctor that he plans to destroy Bashir’s mind bit by bit before finally killing him.
Soon after, Bashir comes across more of the Lethean’s handiwork, encountering a dead Kira and a dying Odo. Before succumbing to his wounds, Odo suggests that Bashir use the conduits to get to Ops quicker. Bashir continues on his way, aging all the while and running into O’Brien. But while this version of the Chief is too fearful to accompany his friend, he nonetheless tells him which path to take through the conduits.
Eventually, he exits the conduits, but despite having followed O’Brien’s directions, he finds himself not in Ops but on the Promenade. There’s a crowd and Quark’s, and when Bashir investigates, he discovers that they are standing around his body, betting on which organs will fail first. The party doesn’t last long, though, as the Lethean appears, kills Quark, and tells Bashir that he’s next. Once again, the not-so-young doctor flees the scene, though he doesn’t get far before he falls and breaks his hip.