Bob & Carol & Ted & Alice(1969)

Overview:

After returning to Los Angeles from a group therapy session, documentary filmmaker Bob Sanders and his wife, Carol, find themselves becoming vigilante couples counselors, offering unsolicited advice to their best friends, Ted and Alice Henderson. Not wanting to be rude, the Hendersons play along, but some latent sexual tension among the four soon comes bubbling to the surface, and long-buried desires don't stay buried for long.