PROOF, by David Auburn

Winner of the 2001 Pulitzer Prize and the 2001 Tony and Drama Desk Awards for Best Play, PROOF is the story of Catherine, a young woman who sacrificed her own education to care for her brilliant, but unstable father, a famous mathemetician.  Now, following his death, she confronts her own emotions, the arrival of her estranged sister, Claire, and her father's grad student Hal, who hopes to discover valuable work in the notebooks Catherine's father has left behind.  In the long weekend following her father's death, Catherine confronts a budding relationship with Hal, the discovery of a mysterious notebook, and the fundamental question of how much of her father's madness -- or genius -- she has inherited.