Convicted on an unspecified crime, Zio was imprisoned in the Akritirian detention facility and fitted with the implant that the prisoners knew as "the clamp". While the clamp drove most of the other prisoners insane or caused them to become extremely violent, Zio spent much time thinking about what its true purpose could be and practicing a technique to ignore its effects, eventually succeeding in ignoring it completely. He also realized that the real purpose of the clamp was not for torture, as most prisoners thought, but was actually a method of keeping the inmate population under control, by turning the prisoners violent and causing them to often kill each other. This realization helped Zio to ignore the effects of the clamp, and he spent his time in prison writing a manifesto of all that he had discovered about the clamp, and his theories about its purpose. While none of the other prisoners were clear-minded enough to learn from Zio's methods of controlling the clamp, his ability to ignore it earned him some respect among the others, and they left him alone.
Around six years into his imprisonment, Starfleet officers Tom Paris and Harry Kim were falsely accused of committing a terrorist bombing and were placed in the detention facility. Zio took little notice of their arrival at first, but was eventually approached by Kim. When Paris was stabbed in a fight with other prisoners, Harry Kim made a deal with Zio: if Zio gave him supplies to clean Paris' wound, Kim would take Zio with him when he disabled a chute so they could escape. Zio was initially refused the offer, but when Kim told him his plan to disable the force field guarding the chute, the prison's only exit, and offered to take Zio with him in exchange for his shelter, Zio reluctantly agreed. As Kim worked to disable the force field, Zio taught him his technique for controlling the clamp to help him focus on his technical work, and explained all that he had realized about the clamp. While Kim was more interested in escape than in theories about the clamp's real purpose, Zio continued to assist him in controlling it. After disabling the force field that protected the chute, Zio and Kim discovered that the hatch opened into space, and that the prison which they thought was an underground facility was really a prison in a huge space station.
Zio abandoned the idea of a fast escape, deciding on a more long-term plan to share his findings about the clamp with the other prisoners and hopefully gather enough of a following to unite them and to escape when a ship docked with the facility to drop off another prisoner or food. Kim however, continued to work on a more short-term solution, still struggling with the clamp. Zio offered to let Kim read his manifesto, encouraging him to put more effort into ignoring the clamp and less into working on immediate escape plan. Around that time, the clamp began to effect the wounded Paris even more, who dismantled the pipe which Kim had been using for his escape plan. After Kim and Paris angrily fought and Kim nearly killed him, Zio encouraged him to finish Paris off, believing that Paris had been driven permanently insane by the clamp, and that he was now nothing but a drain on resources. Kim refused, insisting that Paris could still be saved and that they would be rescued. Zio then forced them to leave his shelter, not having enough resources for both of them. When Kim and Paris were rescued by the USS Voyager, Zio remained in the prison.
Zio was the only inmate who could control the mental effects of the clamp that was placed on each prisoner. During his imprisonment, he occupied his mind with ideas about what the clamp's true purpose was, and eventually discovered it, even without any outside evidence. Due to his ability to control the clamp, Zio was much more clear-minded and sane than the other prisoners, although his focus on his manifesto led Kim to believe that Zio was insane. Zio had an unusual sense of morality, allowing Kim and Paris to use his shelter and resources, and only ordering them to leave after he believed that Paris had gone completely insane. Despite being more merciful and sane than the other prisoners, Zio had no qualms about killing when he deemed it necessary for survival. Paris and Kim witnessed him quickly kill another prisoner for food during a feeding session, something that Zio seemed to consider rather normal. However, unlike the other prisoners, Zio seemed to get no enjoyment out of killing, doing it as a necessity rather than for fun. He told Kim that in order to survive, he would have to become a killer. (VOY: "The Chute")