The Enterprise discovers a wrecked Borg scout ship with a single survivor: a young Borg drone. Dr. Crusher insists on treating the surviving Borg, and Captain Picard reluctantly agrees to transport him aboard the Enterprise.
Given that the Federation was attacked by the Borg, the Enterprise crew are wary of the survivor. La Forge and Data have devised a method to use the captive Borg to destroy the Collective: a geometric formula that is unsolvable, which they plan to show to Hugh for analysis. (The theory is that if Hugh views the formula and then returns to the collective, it will spread throughout every drone in the entire race and act like a computer virus - causing a catastrophic system failure, essentially wiping out the Borg species.) Picard and his crew consider the morality and wisdom of sending Hugh back to the Borg as a weapon of mass destruction. Such an action is questioned by Beverly Crusher, who maintains that genocide should not be considered. Picard notes that with any other race the idea would be out of the question, but the nature of the Borg calls for extreme measures. The Borg drone (played by Jonathan Del Arco), calling himself "Third of Five" (per his position aboard the five-crew scout ship), is dubbed "Hugh" by Geordi La Forge following a conversation of self and Human "designations." Hugh explains that the Borg wish to learn about other cultures and cannot understand why Geordi does not want to be assimilated. The engineer explains individuality, continuing onto the subject of friendship. Geordi begins questioning the act of genocide as Dr. Crusher does. These questions are compounded when Hugh begins displaying traits of individuality. This demonstrated independence raises another question of morality for the crew: Is it right to sacrifice one individual to protect the majority?
Geordi voices his concerns to Picard who dismisses them, suggesting that the engineer "un-attach" himself from the drone. Geordi then speaks to Guinan, whose homeworld was destroyed by the Borg. Despite initial skepticism and revulsion at the idea of naming a drone, Guinan meets Hugh. Her skepticism is called into question when she does not find the expected mindless drone, but a confused young individual who concedes that "resistance is not futile", at odds with the mentality of his people. Guinan urges Picard to meet with the Borg. He does so, and the drone instantly recognises Picard as "Locutus of Borg" so the Captain plays along with this ordering Hugh to assimilate the crew of the Enterprise, including Geordi. Hugh resists the idea, claiming that Geordi is his friend, that the crew do not wish to be assimilated and will resist. When Picard pushes him further, he states "I will not assist you", shocking Picard with his use of the first person singular, and prompting the captain to reconsider his plans.
Picard concludes that it would be immoral to use Hugh as a weapon to destroy his people, and offers the drone asylum within the Federation. Hugh is tempted but realises that the Borg would continue to look for him, jeopardizing the Enterprise. He decides to go back to the crash site and be re-assimilated by the Collective — a plan that Picard theorises may cause disruption of its own, with Hugh's individualism spreading throughout the Collective.
Geordi accompanies Hugh to the crash site and witnesses him being "rescued" and reassimilated. Just before Hugh is transported aboard the Borg vessel, he gives a small parting glance to Geordi.