In desperate need to use the toilet he enters the bathroom while his sister is bathing. Her request for him to wash her back seems natural, and so is what followed.
Bobby's afraid they're going to commit incest. Terri explains why he doesn't need to worry. Then she explains it again. Then she explains it again. And again. And... well, you'll see.
The continuing story of Derek Cutter, a 16 year old who didn't know a lot about sex until his family moved to another town and he began meeting his next door neighbors. In a week's time, it was like he'd earned a college degree in sex ed.