Until September (1984)

"Until September" is a 1984 Drama movie directed by Richard Marquand and starring by Karen Allen, Thierry Lhermitte. American tour guide Mo Alexander misses her tour group, and then her flight out of Paris. Stuck in the city of romance, Mo runs into the very suave -- and very married -- Xavier, who attempts to seduce Mo while his family is out of town. His charms prove hard to resist, and Mo succumbs, though her conscience weighs heavy. Soon their bickering romance of convenience takes a serious turn, and, in spite of himself, Xavier finds he's falling in love.