In "Brokeback Mountain," the 2005 critical hit and cultural flashpoint that won Ang Lee an Academy Award for best director, love is a haunting, elusive ideal briefly attained but forever out of reach. Lee's new movie, "Lust, Caution," which will have its premiere at the Venice International Film Festival this week, is also a tragic melodrama, one in which the lovers are up against forces beyond their control, but it takes a harsher view of romance. This time love is a performance, a trap or, cruelest of all, an illusion.

" 'Brokeback' is about a lost paradise, an Eden," Lee said this month, taking a break from a final sound-mixing session in New York. "But this one ¡ª it's down in the cave, a scary place. It's more like hell."

Based on a short story by the popular Chinese writer Eileen Chang, "Lust, Caution" is set in the early 1940s during the Sino-Japanese war, mostly in Japanese-occupied Shanghai. The heroine, Chia Chi (Tang Wei), belongs to a university drama troupe plotting to assassinate a collaborator named Yee (Tony Leung). Assigned to seduce the target, an official in the puppet government, she falls into a desperately physical affair, driven (as the title suggests) by both passion and suspicion. The cast also includes Joan Chen as the grasping, gossipy Yee, and Wang Lee-hom, the American-born Asian pop star, as the student ringleader. (The film, which will also be shown at the Toronto International Film Festival next month, is set for release on Sept. 28 by Focus Features.)

Lee said that when he first read Chang's story, which she started writing in the '50s then obsessively revised and eventually published in 1979, it struck him in much the same way as the Annie Proulx story that was the basis for "Brokeback Mountain." "At first I thought there's no way I can make it a movie," he said. But he couldn't stop thinking about it. "There's a point where I feel this is my story. It becomes a mission."

Like Lee, 52, who was born in Taiwan but has lived and worked in the United States since the '80s, Chang had a foot in two worlds. Her celebrated early stories and novellas, written in the '40s, evoked the heady, glamorous fusion of East and West, old and new, that characterized Shanghai before the Communist takeover.