Cain came to Hollywood after college hoping to break into music, but instead found himself singing back-up on TV commercials. He switched to acting, originating the role of Matt in the Los Angeles company of "The Fantasticks", as well as appearing on such series as "Room 222", "Lassie" and "Emergency." In the mid-1970's, he raised $80,000 and produced and directed a film called "Elmer", the heartfelt story of a blind boy and an old dog. The film earned Cain enough notice to be assigned two family films, "Brother My Song" and "Buzzard" (both 1976). The following year, he directed and wrote "Grand Jury", about a family caught between the justice system and the mob, and produced, directed and wrote "Sixth and Main", a psychological drama about skid row featuring Leslie Nielsen. But it was with "The Stone Boy", starring Robert Duvall and Glenn Close, that Cain's career began to blossom. The film made many of the year's "Ten Best" lists among critics, and brought Cain together with producer Joe Roth, with whom he would make two other films, including "Young Guns" (1988), which told the tale of Billy the Kid and five other "punks" of the Old West. The film was Cain's first major box office success. But Cain's artistry was far more on display with his other project with Roth, "Where the River Runs Black", based on the novel "Lazaro". Filmed in the jungle of Brazil, the film was not a box office success, but did win much praise for the visuals. Cain has since directed other films, including "Pure Country" (1992), and "The Next Karate Kid" (1994), the first in the series post Ralph Macchio.
Cain has worked infrequently on TV, but did direct the 1990 USA Network movie, "Wheels of Terror". He is the adoptive father of actor Dean Cain, whom he cast in a small role in "The Stone Boy".