[5] In 1945, at age 13, Barrymore and his cousin Dirk Drew Davenport enlisted in the United States Navy to fight in World War II, posing as 17 year olds.[8][9] He was promoted to leading man in just his second movie, the Western High Lonesome (1950), written and directed by Alan Le May, who also wrote Barrymore's next film, Quebec (1951).[10] He starred in The Big Night (1951), written and directed by Joseph Losey, and was in Thunderbirds (1952) with John Derek at Republic.He performed in TV movies, including The Reluctant Redeemer (1954), The Adventures of Lt. Contee (1955), and appeared in several episodes of Matinee Theatre.[13] In 1967, he was cast in the role of Lazarus in the Star Trek: The Original Series episode The Alternative Factor but did not show up on the first day of shooting.Barrymore returned to features with supporting parts in While the City Sleeps (1956), for director Fritz Lang, and The Shadow on the Window (1957).[16] In 1966, Barrymore was signed to play a guest role as Lazarus in the Star Trek episode "The Alternative Factor".[26] Barrymore eventually withdrew from acting, with his final two appearances being a 1974 episode of Kung Fu and an uncredited role in the 1976 film Baby Blue Marine.Although he continued to appear occasionally onscreen, he became reclusive, disappearing into the wilderness to live a mystical existence that has also been described as derelict.He was estranged from his family, including his children, and his lifestyle continued to worsen as his physical and mental health deteriorated.