If you thought Kill Bill, Vol. 1 was tough to follow, just wait until you see 21 Grams, the new movie from Mexican filmmaker Alejandro GonzálezIñárritu. Like his previous work, the critically acclaimed Amores Perros, 21 Grams is an ensemble drama featuring three separate storylines that frequently overlap. This time around, however, the movie unfolds entirely out of sequence; scenes from the end of the flick appear at the beginning, and vice versa. It's disorienting at first, but once you get used to the film's odd rhythm, it all starts to make a strange kind of sense.

So whose bright idea was it to make a movie this way? "I wrote the script with this kind of structure," says the film's screenwriter, Guillermo Arriaga, who also penned Amores Perros. "I felt that it was the best way to tell the story. Some screenwriting teachers say that you must know everything about your characters, but I don't want to know anything about them. I want them to constantly surprise me."

Arriaga's approach certainly surprised the film's cast when they first saw the script. "The first 20 pages were kind of hard to read," confesses Naomi Watts, whose performance is garnering Oscar buzz. "You understood it wasn't linear and you hoped that it would come together somehow. And it does at the exact point you want it to."

Co-star Benicio Del Toro had a similar experience. "I don't know if I understood it completely," he laughs, "but there was something very interesting about it. It reminded me very much of William Faulkner."

Fortunately for the actors, the movie wasn't filmed in the manner it was written. According to Watts, Grams was shot in chronological order, so the actors always knew exactly what was going to happen next. But Arriaga, for one, is confident that viewers will stick with the film. "The first 15 minutes can be very confusing, but I challenge the spectator to stay involved. The fragmentation becomes an emotional experience for the audience and they participate in the film much more."