There's a key casting decision in "Michael Clayton" that instantly raises this film above nearly every Hollywood thriller this year — and it isn't George Clooney, good as he is. Smartly written and directed by Tony Gilroy (screenwriter of the "Bourne" movies), "Michael Clayton" is the story of a "fixer" (Clooney), a former prosecutor employed by a law firm to clean up their messes. When one of the firm's lawyers (Tom Wilkinson) seems to fall apart during the negotiations for a settlement involving an agrochemical company's potentially dangerous product, Michael is called in to calm things down. Soon, he's facing off with the chemical company's chief counsel, Karen Crowder (Tilda Swinton).

In a typical Hollywood thriller, the role of Karen might be played by a pretty up-and-comer, or by a young star (Katie Holmes playing a lawyer in "Batman Begins" comes to mind) seeking to enhance her credibility. But by putting Swinton in the role, the entire chemistry of the film changes: It's not a star vehicle for Clooney (even if the trailers make it appear that way) but an actors' showcase.

Swinton, with her pale-as-paper skin and eerily precise diction, is a unique and arresting presence, and she seems to go through her entire screen time in this movie without taking a deep breath. Her character is tightly wound, newly promoted and a little terrified. At the beginning, we see her rehearsing speeches in her bathroom mirror, carefully intoning meaningless corporatespeak, gradually smoothing her glassy words like wrinkles being pressed out of silk. Karen almost believes what she's saying — if you don't look too closely at her eyes. For an actress who's often called upon to convey steely, scary strength (see her White Witch in "The Chronicles of Narnia" or her jilted lover in "Broken Flowers"), it's a performance of great vulnerability, and its details are fascinating to watch.

But it's not just her movie; Gilroy's cast does fine work all around. Wilkinson is wonderfully unhinged as a lawyer gone off the rails as he realizes the possible damage done by the company he's defending — "I have blood on my hands! I am Sheba, the god of death!" he blusters, all King Lear-ish in the wind. Sydney Pollack, as Michael's boss, is wryly funny. And Clooney, that most effortless of movie stars, gives a smart and perfectly pitched performance as the center around which the others swirl. This is Gilroy's first film as director; I can't wait to see what he's got next.

Moira Macdonald: 206-464-2725 or mmacdonald@seattletimes.com