Proof focuses on Catherine, a young woman who has spent years caring for her unstable father, Robert. Robert was a brilliant mathematician in his younger years, but later became unable to function without the help of his daughter. His death brings Hal, a former student of Robert, into Catherine's life. She ends up falling in love with him, but in the process gravely misses her deceased father while resenting the great sacrifices she made for him. Catherine seems to have inherited her father's brilliance as well as his instability.