How to Save a Marriage (and Ruin Your Life) plot
"The wife you save... may be your own!"
When David Sloane (Dean Martin) learns that his friend Harry Hunter (Eli Wallach) is cheating on his wife, he wants to help him solve it. David thinks Harry is having an affair with his secretary Carol Corman (Stella Stevens) and to avoid that, he starts hitting on Carol himself. But David has taken advantage of his seduction skills on the wrong lady, as Harry is actually dating Muriel Laszlo (Anne Jackson). So when David tells him he stole his mistress, Harry doesn't think of Carol, but of Muriel. And when Harry makes amends with his wife, and Carol and Muriel run into each other, the two gentlemen are in big trouble.