The movie version of David Auburn's Pulitzer Prize-winning play "Proof" doesn't open up a whole lot of the action or provide many specifically cinematic flourishes. But it does deliver exactly what made the stage version so popular: Intelligent middlebrow entertainment with a few juicy roles to feed talented actors.

Taking the most advantage is Gwyneth Paltrow, who turns in her most memorable work since her Oscar-winning turn in "Shakespeare in Love" (which was directed by "Proof" helmer John Madden). She played the pivotal role of Catherine in the London stage production, and she revives it here with a feel for raw emotion that illuminates her character's central anxiety.

Catherine is afraid of following in the footsteps of her father (Anthony Hopkins), a brilliant mathematician who went mad after making ambiguously explained but revolutionary breakthroughs in his field as a young man. Catherine has been caring for Dad in their spacious Chicago home, and when he dies (before the story begins) she fears she'll inherit the mental illness that laid him low.

Madden and Paltrow do a fine job of bringing this fear to life; they do an even better job of dramatizing the internal barriers Catherine must break before claiming her life as her own. Depressed and inert, prone to "Hamlet"-like episodes of conversing with her dead father, Catherine is convinced she'll spiral down if she accepts her own considerable mathematical talents. These fears are born of both loyalty to her father and dread of ending up just like him, a conflict that emerges with impressive clarity in the film.

Hopkins has his share of vivid moments in Catherine's flashbacks, including an "all work and no play makes Jack a dull boy" episode that drives his daughter even deeper within herself. But Paltrow gets most of her assistance from Jake Gyllenhaal, as graduate student-love interest Hal, and especially from Hope Davis, as Catherine's sister Claire, who offers her own obtuse brand of love and support.

Paltrow and Davis share the film's finest scenes as they develop a tense and believable sisterly dynamic. Claire sees herself as the responsible one, even though Catherine stayed home to take care of Dad while Claire followed her career to New York, where she wants to take Catherine. Davis, an underrated actress who always seems to find her way to plum roles, exudes the loving hostility of a sibling who thinks she knows best, even as we think she doesn't quite get it. She's every bit as worthy of Oscar consideration as Paltrow.

For a film largely about madness, "Proof" never takes full advantage of a medium ripe for visualizing subjective experience (see "Spider, "A Beautiful Mind" or, going back further, Roman Polanski's "Repulsion" and "The Tenant"). It's not a particularly adventurous film, but it excels in crystalizing the play's themes and dramatic shifts, and Madden knows when to get out of the way and let the actors do their thing.

When Paltrow unleashes her emotional range and carries Catherine's internal conflicts on her face and in her body language, she shows why she remains an actress capable of lighting up the right role.