ENT Season 2 Episode 22 Cogenitor

Plot

While exploring a hypergiant star, Enterprise makes first contact with an advanced and very friendly alien race known as the Vissians. The two starships' crews are happy to intermingle. Commander Tucker becomes intrigued when he meets a Vissian couple in the mess hall accompanied by a third member of their race, and learns that the being, which has no name, is a "cogenitor" - a third gender in Vissian biology. Cogenitors are needed to complete reproduction: they do not genetically contribute to offspring, but supply an enzyme required for fertilization. Since cogenitors only constitute 3% of the population, Vissians must apply to have a cogenitor assigned to them when they intend to conceive a child. Cogenitors are considered mentally deficient, and are not citizens on equal terms with men and women.
Elsewhere on the ship, Lieutenant Reed finds himself the romantic focus of a female Vissian crewmember - their tactical officer. Captain Archer bonds with the alien captain while on a three-day reconnaissance of the star in a small probe. Tucker becomes increasingly intent on the rights of the cogenitor and learns, with the help of Doctor Phlox, that they are actually equally intelligent. On the alien vessel, without the couple's knowledge, Tucker secretly encourages the cogenitor to learn to read, while building a friendship with them. Despite having a near-total lack of education available, the cogenitor is an insatiable learner. Soon learning the importance of names, the cogenitor asks to be called Charles (Commander Tucker's own first name). Tucker entertains the cogenitor on the Enterprise, showing the cogenitor the 1951 movie The Day the Earth Stood Still.
'Charles' soon realizes that future life in Vissian society would be unfulfilling. The cogenitor requests political asylum. Archer now returns to find himself in the middle of a first contact diplomatic crisis, with the Vissians confused and defensive at Tucker's interference in their traditions. Tucker appeals to Archer's sense of justice, but he sides with the Vissians. With the cogenitor returned, the Vissians hope good relations with the humans can continue. Later communications reveal that Charles has committed suicide, thereby delaying the birth of the child and straining the relations between the two species. Archer summons Tucker and severely reprimands him for his lack of professionalism and judgment.