Harvey possesses a fanciful quality, occasionally demonstrating ingenuity in its depiction of innocence and the importance of safeguarding it from a harsh, self-serving reality. James Stewart portrays Elwood, a good-natured, agreeable man who enjoys alcohol—though we never witness him consuming any. He’s a kind individual who appreciates conversation, so skilled at listening that people readily confide in him with their aspirations, longings, and troubles, treating him as if he were the local priest. Elwood's sister, Veta Louise (played by Josephine Hull), is determined to secure a marriage for her daughter, Myrtle Mae (Victoria Home), but Elwood’s interactions with Harvey—a six-foot-tall invisible rabbit—present an obstacle. Veta resolves to have Elwood institutionalized; however, a chain of unfortunate events leads to her own confinement instead before the mistake is rectified, resulting in further comedic situations. Ultimately, she acknowledges that she prefers her brother exactly as he is.

Source on TMDB