Stardate not given: While a Romulan delegation is reviewing the Defiant's sensor logs of the Gamma Quadrant, O'Brien is recovering from a slight radiation poisoning. All of a sudden the chief engineer seems to hallucinate how another O'Brien is talking to Quark. Five hours later, however, this conversation really takes place. Dax theorizes that the radiation exposure makes O'Brien shift forward in time. The second time shift occurs, and O'Brien finds himself in a brawl between Romulans and Klingons in Quark's bar, which actually happens five hours later. In the third time travel O'Brien witnesses how he is killed when opening a wall panel in a corridor. The Klingons will place a device there to spy on the Romulan delegates. His fourth time shift leads O'Brien to sickbay to find his dead body. Future Bashir sends him back with the advice for present Bashir to care about O'Brien's basilar arteries to save him. After Dax has found out that a quantum singularity triggers the frequent time shifts, O'Brien shifts once again and finds himself on a crowded runabout from where he sees how Deep Space 9 explodes and the wormhole collapses. In order to arrive at an earlier date to find out what destroyed the station, Dr. Bashir gives O'Brien a device that floods his body with delta isotopes to trigger the time shift, although it could be too much for him. In the future it becomes clear that a cloaked Romulan Warbird, which uses a quantum singularity as its power source, is responsible for the attack. The weakened time-traveling O'Brien hands over the device to his future self who travels back to warn Sisko. The commander locks torpedoes onto the quantum singularity, and the Romulans choose to retreat.

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