An injured member of the dangerous cybernetic race known as the Borg is discovered by the Enterprise crew and brought aboard for examination. During the following interactions, they rethink their attitude towards the Borg.
The Enterprise discovers a wrecked Borg scout ship with a single survivor: a young Borg drone. Dr. Crusher insists on treating the surviving Borg despite the past death and destruction the Borg have caused within the Federation. Captain Picard is extremely concerned, but allows Dr. Crusher to continue, assuring that the Borg is confined and monitored by security forces at all times as long and unable to contact the Borg Collective.
Chief Engineer La Forge and Commander Data assist Dr. Crusher in bringing the Borg back to health. As they come to understand the workings of the Borg, La Forge and Data postulate an idea of using the Borg drone as a weapon of mass destruction; by implanting an unsolvable geometric formula into his mind, and returning him back to the Collective, the formula should rapidly spread similar to a computer virus and disable the Borg. Dr. Crusher is aghast at this suggestion, considering it equivalent to genocide, while Picard and the other senior crew deliberate on the ethics of this plan.
The Borg eventually gains consciousness. Initially calling himself "Three of Five", he ends up naming himself "Hugh", misunderstanding when the crew address him as "you". Hugh discusses how the Borg only wish to learn about other cultures through assimilation, but La Forge counters, discussing aspects of individuality that make them human and unique. In further debates, La Forge finds himself becoming a friend to Hugh, and begins to doubt his previous idea of genocide. This is further complicated when Hugh shows elements of individualism. The crew now debate whether it is appropriate to sacrifice one individual to protect the majority, though Picard is still insistent on destroying the Collective.
Finding Picard to be unwavering on the plan, Dr. Crusher and La Forge arrange to have Guinan, who has a similar detest for the Borg as they had destroyed her homeworld, speak to Hugh. Guinan finds Hugh not to be a mindless drone, but a young confused man, and agrees Hugh is no longer a Borg. Guinan convinces Picard to visit Hugh, where he finds the same conclusion, including hearing Hugh refer to himself as "I" instead of the Borg's collective "we". Recognizing Hugh as an individual, Picard abandons the proposed plan and instead offers Hugh asylum within the Federation, but Hugh refuses, recognizing that the Borg will still come looking for him. Instead, Hugh offers to be returned to the crash site, to be found and re-assimilated by the Borg later, with hopes that the sense of individualism that Hugh has come to learn will spread through the Collective.
La Forge accompanies Hugh to the crash site, and from a safe distance, watches the Borg recover him. Just as the Borg transport out, Hugh turns to give La Forge a parting glance.
Jonathan Del Arco had no concept of what a Borg was prior to the audition. He received his script on the evening prior to meeting with the producers and felt that it gave him a decent sense of the character. At the audition, there were another 10 to 15 actors, and they were each talking to each other and saying that they weren't sure how to undertake the role. Instead, Del Arco later explained that he was deliberately anti-social in order to get into Hugh's mindset. When he performed for the producers, someone else read the lines assigned to Picard and La Forge, and he felt like he immediately got a positive result. He received a call back, and return to audition once more. He said that his performance in "I, Borg" was driven by the memories of watching a childhood friend die, and the innocence that he felt given to his friends memory over time; "When I first read the script. I heard his voice, that's what it sounded like - full of wonderment and confusion about everything. That, to me, was Hugh." Following his appearance in the episode, he later pitched a couple of story ideas to the producers to feature the return of Hugh. He was happy when the character later returned in the sixth season finale/seventh season opener "Descent", which he felt was similar to his previous ideas.