While having an affair with my sister's friend, my sister found out

Nick Strokes is fucking his stepsister Molly Little when Nick's girlfriend Penelope Kay walks in. Penelope storms out, and Molly asks Nick to follow her. When Penelope sits down to explain everything, she makes it clear that she wants Nick to talk about how he would have sex with Molly to fulfill his own family fantasy, not to actually do it.