"Side Effects," Steven Soderbergh's tightly wound mind game, is definitely worth playing. It stars Jude Law as Dr. Banks, a psychiatrist counseling a suicidal young woman named Emily, played with great detachment by Rooney Mara. Emily gets only worse, until the doctor switches her meds. The upside, the depression lifts; the downside, Emily may have killed someone while sleepwalking, the result of a rare side effect. Soderbergh allows us to get as comfortable with the facts as Banks. Then he devilishly pulls the rug out from under us. It's fascinating to watch the doctor scramble to unspool what really happened. Screenwriter Scott Z. Burns is no help at all, having concocted countless treacherous switchbacks. Meanwhile, Soderbergh keeps the pace brisk and the therapy-speak in perfect check. The side effect is a first rate brain tease.