Just in case you haven't figured it out yet, this is a hilarious little story about a guy who's been having sex with his sister's girlfriend. It's all very well and good, but it's not all that funny when you think about it. The guy's got a lot going for him, but he's also a little worried about what his sister-in-law is going to think of him. He's worried that she's going to freak out when she finds out that he has sex with her. He also worries that he'll get caught for it.