Ang Lee's follow-up to Brokeback Mountain is flawed, but Lust, Caution (an erotic spy thriller set in 1940s Shanghai) is so ambitious and detailed that you'll never be bored. From the clinking of lacquered nails against mah-jongg tiles to the thrill of a first cigarette, Lee envisions a world where sensuality is the engine that fires not just youthful rebellion, but politics, assassination plots, maybe even torture. It's provocative by design. (See Movie Times for details.)