How to Save a Marriage and Ruin Your Life (1968) 1080p Dean Martin, Stella Stevens, Eli Wallach

Battle of the sexes comedy about a freewheeling bachelor who decides to save his friend s marriage by proving that all mistresses are incapable of fidelity. The plot gets complicated when the bachelor offers to set up the wrong girl in a lavish lovenest and she accepts, thinking it to be a marriage proposal.