Caught in the act: Such perceived elder mothers as grandmothers and other experienced elderly women liking to get dirty

A couple is caught by their 18 year old daughter while they are on a sexcapade dressed elaborately as figures of the opposite sex. The young woman follows the lead which turns out to be a very horny threesome between her and her grandparents. Sensual combination of Dirty Old Man trope and sexual attraction of experienced woman to a young man.