I'm not into incest but the actual storyline in the the movie is that young Tom is talking to Mrs. Hunnicutt about a summer job... Maybe mowing her lawn. But Mrs. Hunnicutt (the voracious Tantala) has other ideas about how she might use his services over the summer and gives him a try-out. Definitely one of my favorite classic era scenes.
This is a scene from the 1985 video "Sounds of Sex", produced and directed by Billy Thornberg. They don't make porn like this anymore! I wish they still did, now that porn is so readily available on the internet. Today's porn cannot compare to porn back then. Back then, porn was not pure sex. Back then, there was a plot, a storyline, like there would be in any movie. That made porn back then SO much hotter than porn today!