From the liner notes

A kinky mother and daughter are having lots of fun living together with Mom’s second husband. As a family, they live by the rule that the family that stays together does everything together. But when Mom’s first husband returns from a long trip and finds out about what’s going on on the home front, he blows a fuse and tries to prevent his daughter and her mother from continuing to live with the swinging step-dad.

Not wanting to disrupt a good thing the daughter talks a girlfriend (who she has the HOTS for) into a little trick against her Dad, who does not know what she looks like as an adult. The girls leave Dad high & dry and upon understanding the ruse Daddy dearest decides not to try to gain custody after all they really are Like Mother, Like Daughter!