Bob and his wife Carol are a sophisticated California couple who attend a secluded institute for group therapy. Their original intention is to merely observe, but they become so involved that they decide to test the strength of their marital trust and honesty by experimenting with mutually tolerated affairs. Ted and Alice are their closest friends who find themselves continually amused at the latest Bob & Carol sexual adventures until finally they are invited to liberate themselves in a one-bed menage a quatre.