Archer is thrilled to be within ten light years of a hypergiant star. As the crew prepares to study the phenomenon, they make first contact with another species — the Vissians, who are also in the area to study the hypergiant. After the Vissian captain, Drennik, explains that meeting new species is one of their primary goals, Archer invites him and his crew onboard Enterprise for dinner. Once there, Drennik and Archer hit it off, and Drennik invites Archer to join him when he takes the Vissian stratopod deep into the hypergiant the following day. Archer enthusiastically accepts the invitation. Meanwhile, other crewmembers are mingling with the Vissians. Reed hits it off with a female Vissian tactical officer, while Trip meets the Vissian chief engineer and his wife. Trip is intrigued by a third individual the couple has with them, a member of the species' third gender known as a "cogenitor." The cogenitor is a nameless individual who somehow makes pregnancies among Vissians possible — the engineer and his wife are trying to have a baby.

The Vissian engineer invites Trip to explore the engineering department on the Vissian ship. But, while there, Trip can't help but ask questions about the cogenitor. In an effort to learn more, he accepts a dinner invitation from the engineer and his wife. As they talk over dinner, Trip can't help but feel that the cogenitor is mistreated. The Vissians seem to think of it as something less than a pet, and it is not allowed to attend school or learn. With help from Dr. Phlox, Trip surreptitiously scans the cogenitor, and learns that it has the same mental capacities as the other Vissians.

Meanwhile, other Enterprise crewmembers are forming close bonds with their new Vissian acquaintances. Archer and the Vissian captain come to be friends as they pilot a small Vissian craft through the hypergiant, while Reed forms a romantic attachment to the Vissian tactical officer.

Trip, however, is becoming close to the cogenitor. After determining that it has the same mental capacity as other Vissians, he attempts to help it by secretly teaching it to read. He tries to encourage it, telling it that it has the same abilities and rights as other Vissians. He even goes so far as to invite it onboard Enterprise for a tour, and introduces it to such concepts as movies and games. The more the cogenitor learns, the more excited it is about the prospect of being able to live a fuller life. Unfortunately, the other Vissians don't feel the same way. Once they learn of Trip's secret encounters with the cogenitor, they inform him that he is no longer welcome on their ship. The cogenitor, meanwhile, asks Trip for refuge on Enterprise.

When Archer returns from his adventure with the Vissian captain, he is furious at Trip for interfering in Vissian affairs. However, he knows that he must take the cogenitor's plea for asylum seriously. After a meeting with the Vissians and further thought on the matter, he eventually decides that he must send the cogenitor back to the Vissian ship. As the captains bid farewell, the Vissian captain mentions that he hopes the incident won't tarnish the two species' future relationship.

Then, a few days later, tragedy strikes. The Vissian captain contacts Archer — the cogenitor has committed suicide. Angrily, Archer expresses his displeasure at Trip's actions. Trip realizes that his role in the cogenitor's education means that he is responsible for her death. Shaken, he can only ponder his actions and their consequences.