Stretching 700 miles from top to toe, Italy has a north and a south, a winter and a summer, a head and a heart. The forbidden romance "I Am Love" is rooted in the chill of the affluent north, blooms in the warm countryside — then grows insufferably thorny in the place where all love ends.

It's a long if lovely road, with fewer volcanic peaks than in the midcentury melodramas it emulates. It takes 50 minutes for the first shoe to drop, when Emma (Tilda Swinton), the Russian-born wife of a Milanese industrialist, is startled by her attraction to her son's best friend, an earthy young chef named Antonio (Edoardo Gabbriellini).

That shoe is a glass slipper. Director Luca Guadagnino and the tremulous Swinton slowly weave the notion that the happily married Emma is actually a sad Cinderella, closer to the servants at the family villa than she is to her rich husband, Tancredi (Pippo Delbono).

Since Tancredi plucked her from a Russian garden, Emma has learned to speak Italian, supervises the extended clan's elegant dinner parties, and even claims to have forgotten her original name. But a not-quite-chance encounter with Antonio in the seaside village of San Remo leads Emma to the site of his rustic restaurant for some steamy sex à la D.H. Lawrence.

"I Am Love" is often ravishing, but there is less than meets the eye. Subplots about a daughter's lesbian awakening and the sale of the family textile mill allude to themes of freedom and responsibility that are never effectively echoed by the langorous love story.

Guadagnino tries to compensate with a fateful finale, but the overripe ending, heated by the percolating music of John Adams, is heavy seasoning on a delicate dish.

"I Am Love" is easy to savor but tough to swallow.