They All Laughed(1981)

Some of them promised they'd never fall in love.

New York's Odyssey Detective Agency is hired by two different clients to follow two women suspected of infidelity. Ladies' man John Russo trails Angela Niotes, the elegant wife of a wealthy Italian industrialist, while Charles Rutledge and Arthur Brodsky follow Dolores Martin, the beautiful young wife of a jealous husband. Their respective cases are complicated when John falls for Angela, and Charles falls for Dolores.