Captain Janeway tells Seven of Nine that one of the children Seven has been taking care of, Icheb, is going to have to leave the U.S.S. Voyager. Icheb is one of the four children that were liberated from the Borg collective. Voyager's crew managed to locate Icheb's parents and are planning to take him back to them. Seven is upset at this because she has come to think of Icheb as a son.
When they near Icheb's home planet, readings indicate there is a Borg transwarp conduit very nearby and the planet has been attacked by the Borg several times. When Janeway, Seven, Icheb and Tuvok beam to the surface, they meet the planet's inhabitants, the Brunali. They notice that most of the buildings are small huts and the Brunali tell them that have to keep things very low-tech or the Borg will detect them and attack the planet again. The only time the Borg attack is when they think they can get new technology.
When the away team is greeted by Icheb's parents, Luecon and Yifay, Icheb asks to go back to the ship. The away team and Icheb's parents all go back to Voyager and discuss how to make the transition easier but Seven begins to argue with the boy's parents. While onboard, Yifay makes Icheb's favorite meal, which he really enjoys. Leucon explains to Seven that the Borg took Icheb four years ago when he wandered off to see a new fertilization array. Leucon explains how sad he was when he lost the boy.
After spending time with his parents, Icheb decides to stay with the Brunali. He knows that his knowledge of technology can help them rebuild their villages. Seven is sad to see him go.
As Voyager leaves orbit from the planet, one of the three remaining Borg children, Mezoti, cannot sleep because she misses Icheb. As she talks about it with Seven, she mentions that Icheb told her he was taken from a ship, not from the planet's surface. Seven is curious why Leucon had lied to her and begins to research the planet. Her research reveals that the Borg did not attack the planet four years ago, so Icheb could not have been taken at that time. When Seven gives this information to Janeway, the Captain turns the ship around and heads back to the Brunali planet.
On the Brunali world, Icheb's parents grab him and inject him with an alien medical device. The device renders Icheb unconscious and his parents put him on a shuttle heading for the Borg transwarp conduit.
When Voyager returns to the planet, Leucon is defensive and tells them to leave. Harry Kim scans the planet for Icheb's life sign but does not find him. Seven discovers the shuttle heading for Borg space, and Voyager pursues. Seven manages to transport Icheb onto Voyager just as a Borg Sphere emerges from the conduit and traps both the Brunali shuttle and Voyager in a tractor beam. The crew transports a photon torpedo to the shuttle, which detonates inside the Sphere and damages it, allowing Voyager to escape.
The Doctor determines that Icheb had been genetically engineered at birth with anti-Borg pathogens. His parents had raised him specifically to infect the Borg and stop the attacks on their planet. The Doctor is able to suppress the anti-Borg virus, but Seven is not sure she will be able to help Icheb come to terms with what has happened. Seven trusts her maternal instincts and begins to help Icheb understand that on Voyager he has a family that loves him and will never let him go.