It would be tempting to say that fractured time sequences in movies have become a cliché, except that Wicker Park, unjustly lambasted by most critics, makes your brain spin in surprising and pleasurable ways. The hero, a junior ad executive played with a gentle wince of passion by Josh Hartnett, is presented, explicitly, as the most romantic of stalkers. We see him in scenes that take place two years apart: first, when he's working at a camera store and spies a beautiful stranger (Diane Kruger), whom he follows to a dance class, ultimately trespassing right into her heart; and, later, after they have broken up, when he becomes involved with the enigmatic Alex (Rose Byrne), who turns stalking into a form of identity theft. The director, Paul McGuigan (''Gangster No. 1''), layers time so that the past and the present melt, at least in spirit, into one. You have to work, maybe a bit too hard, to follow ''Wicker Park''; I could hear the audience turn off to it the more complicated it got. Yet the final clinch, scored to Coldplay's ''The Scientist,'' is a moving testament to the way that ''normal'' amorous behavior needs, at times, to lurch into obsession. The movie doesn't make the extreme look ordinary so much as it finds one inside the other.