Armando is one of the most renowned therapists in São Paulo. One of his patients, a 17-year-old boy by the name of Sergio, abruptly interrupts his course of therapy after a trip to New York. Sergio's cursory explanation to Armando is that he has finally found his own path to happiness and must pursue it. For years, without any further news of Sergio, Armando wonders what happened to his patient. He subsequently learns that Sergio is living a happy life in New York and that he is now a woman, Sandra. Not long after this startling discovery, however, Armando is shocked to read about Sandra's unexpected death. In an attempt to discover the truth about Sergio and Sandra's life, Armando starts investigating on his own. Sergio Y. is a unique and moving story about gender, identity, and the search for happiness.