"LILY IN LOVE," an update of Ferenc Molnar's classic farce "The Guardsman," remains a charming, but stagy, variation on the love triangle.

The film is a showcase for the histrionic virtuosity of Christopher Plummer in a dual role as an incorrigible English thespian who disguises himself as a courtly Italian film star, only to find himself having an affair with his own wife.

Maggie Smith has the title role of the disgruntled Lily, a playwright who pens a new script for happiness called "Lily in Love," in which a European gentleman romances a married woman vacationing in Budapest. In the past, Lily's stories have starred her husband "Ham," but this time around there's no part for him.

With the help of his longtime agent (Adolph Green), he disguises himself as a preposterous blond Italian, lands the part and regains Lily's heart. In fits of jealousy, he scathingly attacks himself as that "slimy piece of mozzarella," and her as an unfeeling adulteress. It's preposterous, but fun.

Inside film jokes, a weak ending and a sparse background injure "Lily," which seems far more contrived today than it did in the heyday of Lunt and Fontanne, who filmed the original play in 1931. Yet it remains a terribly theatrical good time.

LILY IN LOVE (PG-13) -- At the Key.