Successful, strait-laced Jewish lawyer Harold Fine (Peter Sellers) takes a walk on the wild side after reluctantly agreeing to marry his long-time girlfriend, Joyce (Joyce Van Patten). Unexpectedly smitten by his hippie brother's flower-child girlfriend, Nancy (Leigh Taylor-Young), and her potent, marijuana-laced brownies, Harold ditches his establishment life and embraces communal living with Nancy, only to realize the freewheeling life might not be all that it seemed.