From the moment that Gwyneth Paltrow reunited with her Shakespeare in Love director John Madden for the 2002 London theater production of Proof, tongues wagged about a possible movie adaptation. But it took a bit of convincing to bring the award-winning pair back for a screen version of the haunting play about Robert (Anthony Hopkins), a brilliant but mentally ill mathematician, and his depressed daughter Catherine (Paltrow), who gives up her studies to care for him. ''I don't think [a movie version] is something you want to undertake unless you think that something particular can be gained from it,'' says Madden. ''It's kind of an odd challenge because [the play] is quite interior and quite restricted...but there seemed to me to be a way of telling the story in cinematic terms that was interesting and unusual. Rarely does [a film] take you inside somebody's head.''
For Paltrow, working on the film a year and a half after her acclaimed theater run allowed her to bring more emotional heft to her portrayal of the complex and mysterious Catherine. ''I think that as you have more life under your belt, you're drawn to things that are slightly more complicated,'' says Paltrow. But the life experience she gained in the interim wasn't just from getting older. ''The difference between my stage performance and my movie performance is that my father was still alive when I did the play,'' says Paltrow. ''You don't know what that's like until it happens... I had the first anniversary of his death while we were filming, so it was very, very raw for me.''
Indeed, Catherine's scenes with her unstable father, shrewish sister (Hope Davis), and grad-student boyfriend Hal (Jake Gyllenhaal) are more emotional than you'd expect from a film that's ostensibly about math. ''Those who don't understand [math] think of it as dry, theoretical, concrete, having nothing to do with the imagination,'' says Madden. ''But it's something quite difficult to explicate in a way that music is. Music somehow communicates emotionally, and I felt there was an aspect of [the math] that could translate and could be felt.''