| Gwyneth Paltrow | Catherine |
| Anthony Hopkins | Robert |
| Jake Gyllenhaal | Hal |
| Hope Davis | Claire |
| Gary Houston | Professor Jay Barrow |
| Roshan Seth | Professor Bhandari |
| Anne Wittman | Joanne |
| Leland Burnett | Eddy |
| Daniel Hatkoff | Student |
| John Keefe | Admirer |
| Haroula Spyropoulos | Student |
| Colin Stinton | Physicist at party |
A depressed woman copes with the death of her father, a brilliant but mentally ill mathematician.
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