U.S.S. Voyager encounters a Wysanti starship, the same species as Rebi and Azen. The Wysanti offer to take in Rebi and Azan, as well as Mezoti, leaving Icheb the only other child that Voyager had rescued from the Borg. He and Seven of Nine discuss their feelings about the others' departures, and Seven finds she is crying, and believes her ocular implant is malfunctioning. the Doctor agrees it was a malfunction, but Seven continues to experience headaches and strange feelings.
After successfully completing analysis of a nebula in Astrometrics, Icheb asks Seven for more challenging assignments on the bridge, to which Seven says that Icheb would need to pass the Starfleet Academy entrance exam. Icheb accepts this, and Seven offers to get a letter of reference from Captain Janeway. She finds her hand is shaking, and excuses herself to the cargo bay to attempt to regenerate, but the computer refuses to engage as it states Seven's cortical node is malfunctioning. She tries to go for help, collapsing in the mess hall as other Borg implants begin to appear on her body.
In sick bay, the Doctor reports that they cannot repair the node, and Seven will likely die without a replacement. Discovering a nearby Borg debris field, Janeway, Tom Paris and Tuvok take the Delta Flyer to find a replacement node. They are briefly waylaid by raiders that claim the field as their own, but they manage to chase them off, and leave with a node from a long-dead drone. The Doctor simulates the transplant of the new node into Seven, but each run is unsuccessful, as the node has been inactive for too long. Seven prepares to accept that she might die. Though the Doctor has confined her to Sick Bay, Seven deactivates him and goes to speak to B'Elanna Torres about the nature of death, worried that as she is no longer tied to the Borg collective, her contributions will be lost. Torres assures her that she has helped the crew tremendously, and will have a legacy on Voyager.
Icheb, aware of Seven's condition, offers to give up his cortical node for Seven; as he was not fully assimilated by the Borg, he will be able to survive without it. The Doctor simulates the transplant and agrees it has a high chance of success, but Seven refuses to allow Icheb to do this. Icheb purposely programs his alcove to disengage the node, causing his health to falter. He is rushed to sick bay, but refused to allow treatment to remove the node unless Seven is willing to accept it; Seven remains steadfast she refuses to take the node. Janeway, Seven, and Icheb debate, but eventually all agree to allow Icheb's node to be removed and used to replace Seven's. The operation is successful, though Icheb must spend several days in sick bay to regain his health. Seven tells Icheb his actions were foolish and emotional, but then thanks him, and promises to help him prepare for the Academy entrance exam. Icheb agrees, and Seven finds she is crying once more, though her new node is functioning perfectly.