A promising first contact between Enterprise NX-01 and the Vissians that ended in tragedy after Trip Tucker taught a member of the Vissians' third sex, treated as property, to read.
In the Enterprise episode Cogenitor, the ship meets a friendly and more advanced Vissian vessel while studying a hypergiant star. Captain Archer goes off on a survey flight with the Vissian captain, Drennik, and the two crews mix freely.
Tucker learns that Vissian reproduction needs a third sex, the cogenitors, who make up a small part of the population and are passed between couples without names, education or rights. Convinced that the one aboard is as intelligent as anyone, he secretly teaches it to read and shows it films and the ship.
The cogenitor asks Archer for asylum. Archer refuses, unwilling to impose human values on a people he has only just met, and returns it. Soon afterwards the Vissians report that it has taken its own life. Archer tells Tucker bluntly that he bears responsibility.