Kes returns a vengeful woman bent on destroying Janeway and Voyager. Using her advanced mental abilities, Kes journeys into the past, intent on delivering the crew into the hands of one of their earliest and most dangerous enemies.
Voyager receives a distress call from a small vessel, piloted by a much older and weathered Kes. Captain Janeway grants her permission to come aboard, but she comes in much too fast and the vessel collides with Deck Nine. However, Kes beams herself aboard Voyager just before impact.
Aboard Voyager, a cold and angry Kes uses her psychokinetic abilities to disable Voyager's systems. Voyager is in red alert as Kes gives off high levels of neurogenic energy. A security guard fires a phaser at Kes as she heads toward Engineering. She is hit by the blast and when she recovers she screams in anger, causing the bulkheads around them to blast inward in an explosion of fire and debris.
Armed with phasers, Torres and Seven of Nine are shocked when the weapons ripple and distort in their hands. Kes places her hands upon the warp core. Just as Torres goes to shut it down, she is struck in the back by a tendril of energy. Seven rushes over to Torres' dead body, while Kes vanishes in a flash of light.
When Kes disappears, she travels backward in time to Voyager as it was five years earlier. It's only been a few weeks since Voyager was pulled into the Delta Quadrant. Sneaking up behind the original Kes, the undetected Kes from the future injects her with a hypospray, rendering her unconscious.
Janeway is concerned that another conflict may soon ensue with the Vidiians since two more ships have been detected on long-range sensors. On a secure channel, Kes from the future makes contact with the Vidiian Captain. She tells him she will provide him with information necessary to capture Voyager, in return for her safe passage home to Ocampa.
Meanwhile, Tuvok seems to be experiencing premonitions. While walking down a corridor, he sees a young girl working a wall console that turns out to be Naomi Wildman. Tuvok follows the girl into the Cargo Bay, and when the doors open he sees Seven of Nine and the Borg Twins regenerating in their Borg alcoves.
The Doctor confirms for Captain Janeway that Ensign Wildman is expecting a baby girl. Back in Engineering, Tuvok is once again having visions of the future. This time he is watching a fragmented replay of events that have already occurred in the future, when Torres is struck in the back with an energy tendril as a much older Kes looks on. Tuvok is brought to Sickbay where he begins to convulse upon the surgical bed.
Janeway decides to view the proximity scan of Tuvok at the time he collapsed in Engineering. Apparently there was a surge of tachyon particles in Engineering just before Tuvok collapsed. Janeway suggests that tachyons are normally generated by temporal distortions, also known as time travel.
Chakotay discovers that tachyon readings are being emitted in Sickbay, the Airponics Bay and Kes' quarters. Suddenly, Voyager finds itself under attack by the Vidiians. Paris is shocked that the Vidiians know so much about Voyager, including when they would be coming out of warp, as well as their shield frequencies. Kim detects transmissions to the Vidiians originating from Voyager on Deck Ten.
The Vidiians have managed to board Voyager upon Deck Eight. Voyager's only chance is to explosively decompress that section of the ship. In a violent explosion, the Vidiian grappling pylon is blasted away from the ship.
Janeway and Kes from the future come face to face. Janeway instructs Chakotay to redirect all plasma flow on Deck Eleven to the Shuttlebay command console. Arcs of energy course up Kes' arms and into her body. She begins to convulse violently and then falls dead to the floor.
When an older Kes hails Voyager again in the future, the crew is already prepared. This time Captain Janeway shuts down the warp core completely. Kes from the past appears to the older Kes in a message that she recorded to herself five years earlier. She reminds the older Kes that she didn't always harbor so much anger toward the crew. Janeway tells her that the Voyager crew is not her enemy and that there is always room for her. However, according to Kes, there is no place for her anywhere. Altering the chemical composition of her body, Kes begins to dissipate and then vanishes.
