During the night shift, as Paris presses Kim to join him on a double date, the ship is shaken by a huge shockwave. Investigating its origins, the crew finds a nearby planet where a cataclysmic explosion recently wiped out all life. Beaming down, the Away Team discovers that the detonation has actually fractured subspace. But before they can react to this dangerous revelation, Paris and Janeway find themselves transported back in time to the day before the explosion.
While the crew tries to figure out how to retrieve the missing officers, Janeway orders Paris not to warn the residents of the planet about the approaching disaster, since that would violate the Federation's Prime Directive. Seeking their own way back to Voyager, the pair head for a polaric ion power station, the site of the future explosion. There, they inadvertently become caught up in a clash between the authorities and a group of protesters who later accuse them of being government infiltrators. Disbelieving Janeway's claim that they are about to trigger a major accident, they continue to move forward with their plan to sabotage the power station.
In the meantime, a troubled Kes reveals that her latent Ocampan psychic abilities seem to have been sensitized by the accident. She accompanies the Away Team as they attempt to track Janeway and Chakotay's movements being made in the past.
The protesters force Janeway and Paris to accompany them to the plant, where they shoot their way in. Paris is wounded during the scuffle, but Janeway leaves him to follow the protesters, hoping to stop the devastating explosion.
On Kes' recommendation, Chakotay's crew goes to the flashpoint of the blast and uses a polaric beam to "cut through" subspace and find the missing crewmembers. When Janeway sees their polaric beam, she realizes that it wasn't the protesters who caused the accident — it was the Away Team's attempt to rescue her! Janeway uses her phaser to blunt the impact of the beam. At the instant she succeeds in sealing the opening, time is "reset," and the crew finds itself back on Voyager, a few seconds before the shockwave first hit the ship. None the wiser for their experience, Paris urges Kim to join him on a double date, and Kes finds herself strangely relieved that a nearby planet is teeming with life.