He - Yee (Hong Kong star Tony Leung) - is in the secret police, a collaborator with the occupying Japanese, a married man. She - Mrs. Mak (Tang Wei) - is likewise wed, or so she says. In fact, she is a young woman, only a few years out of university, who has banded with a group of theater students-turned-resistance fighters. Her mission, should she choose to accept: Seduce Yee, lure him from his security detail, and have him killed.

A rich, beautifully detailed espionage thriller that captures the bygone days of Shanghai, "Lust, Caution" also is one of those rare movie experiences: Its scenes of the trysts between Yee and Mak, from their rough-stuff first encounter to the long, tangled love-making sessions of subsequent meetings, are truly erotic. With an unblinking camera and bold performances by Leung and Tang, these scenes - which make up maybe a dozen minutes of Lee's 2 hour, 37 minute drama - are not only what the film pivots on. They are what the conflicted souls played so exquisitely by Leung and Tang turn upon as well. (The scenes garnered the picture a rare NC-17 rating.)

Later, Lee turns a couple of lovely scenes with Wong losing it at the movies, weepily watching Ingrid Bergman in "Intermezzo," paying for a ticket for "Penny Serenade."

Also very good in "Lust, Caution" is Kuang Yu Min (the Asian pop star Wang Leehom), as the leader of the theater company and of the resistance cell - a man clearly troubled by the lengths he's asked Wong to go to insinuate herself into Yee's world. And troubled by his own feelings of jealousy and desire.

Joan Chen, in a quiet, tamped-down role, plays Yee's wife, passing her days shopping, gossiping and playing endless hours of mahjong with her girlfriends - one of whom is the spy who calls herself Mrs. Mak.