When Voyager encounters a seemingly friendly alien ship its crew has never seen before, the Nasari, Ensign Kim instinctively fires Voyager's weapons upon it without orders. Harry claims that a tetryon surge being emitted by the ship was the aliens preparing to attack them. Voyager sustains heavy damage while battling the enemy but manages to make them withdraw. Kim is relieved of duty, pending investigation of his overtly hostile actions. Janeway later confirms that Harry's "instincts" were correct, that the ship was indeed preparing to attack. Harry recounts other episodes of déjà vu since entering that region of space.
Later that night he has a strange dream, and when he awakens, he discovers a strange reddish rash on his head. The Doctor cannot find an initial cause. When the Nasari return with more ships, Harry's instincts tell him to flee to a nearby planet where they are defended and then hailed by the Taresians.
Captain's log, stardate 50732.4. The Taresians have escorted us back to their home world so we can continue to investigate their claim that Ensign Kim is a member of their race.
Once on the planet, the Taresians attempt to explain Harry's strange behavior. According to them, Harry is Taresian and was sent to Earth as an embryo where he was implanted into his "human mother." He took on the genetic traits of his human parents, but was programmed with both genetic knowledge and an urge to one day return to Taresia. When he entered the Taresian region of space, his dormant Taresian genes began to reactivate, explaining his current behavior. Harry befriends another male Taresian and learns that the planet's population is 90% female, and that males are very rare and thus very valuable and prized.
While Harry remains on the planet in an attempt to better understand his recent changes, Voyager leaves to attempt to make contact with the Nasari and negotiate safe passage from the system. Harry learns that because males are so rare on Taresia, he is valuable breeding stock. He attends the marriage ceremony of his new male friend who is bonded with three Taresian females. On Voyager, the doctor discovers something strange about Harry's DNA: it was implanted, possibly by a virus, and it is not natural to his body. Janeway also realizes that a defensive grid has been raised around Taresia preventing them from communicating with Harry or transporting to the surface.
After spending the night on the planet, Harry suffers more strange dreams which cause doubts to begin creeping into his mind. Two very "interested" females attempt to calm him, but he resists their attempts. Now outright suspicious, Harry goes to see his male friend. When he enters his quarters he discovers the desiccated remains of his friend. He is confronted by several females where they reveal the truth to him. He was not born on Taresia. Because natural born males are so rare, the Taresians devised an "artificial" way to procreate their species. They implant Taresian genes into male members of other species which rewrites their DNA and makes it compatible with Taresian females. Even more horrifying is that the "reproductive process" means draining the males of their DNA where it is then implanted into females, causing the death of the males. As a result, new males are constantly "created" and harvested.
Harry attempts to flee and is pursued by many females and their leader. Just when they are about to capture him, Voyager penetrates the grid and beams Harry on board. They flee the system with a Taresian ship in pursuit. The Nasari then appear but instead of attacking Voyager, they attack the Taresians instead, allowing Voyager to warp away. The Doctor is later able to extract the foreign DNA and successfully returns Harry to his true human form.