An omniscient narrator introduces us to Mr. Rose, chasing butterflies in San Francisco's Union Square. Rose is not content to collect bugs; he's also a prude and a scold, staging a one-man campaign against the city's adult entertainments. He defaces photographs, complains by phone and letter to city hall, disrupts live performances and fowls film in projection booths. Then, at a nightclub featuring belly dancers, Rose is dispirited by the lascivious behavior of young people in attendance. While Rose is disheartened and vulnerable, Satan pays him a visit and tempts him into a life of dissolution. Will Rose remain pure or will he succumb and become the erotic Mr. Rose?