Based on the Pulitzer Prize-winning play by David Auburn, "Proof" follows a devoted daughter (Paltrow) who comes to terms with the death of her father (Hopkins) - a brilliant mathematician whose genius was crippled by mental instanity - and is forced to face her own long-harbored fears and emotions. She adjusts to his death with the help of one of her father's former mathematical students (Gyllenhaal) who searches through her father's notebooks in the hope of discovering a bit of his old brilliance. While coming to terms with the possibility that his genius, which she was inherited, may come at a painful price, her estranged sister (Davis) arrives to help settle their father's affairs.