A Foreign Girl in Paris (1981)

While his wife is temporarily out of town, Richard meets a pretty blonde tourist by a fountain; they hook up and have various sexual experiences, including with a prostitute, a stripper in a nightclub and a friend of Richard's and his wife, and an orgy. When Richard's wife returns from her trip, he is in for a surprise--it turns out that she knows Richard's blonde tourist "friend". And that's not all she knows.