From the introduction:
It is another text from your sister-in-law, Shelby. A moment later, she sends you a picture. It shows Shelby standing in her bathroom, topless, so you can see her perfect round breasts. Her long blonde hair is down and frames a young face. She is wearing pastel colored panties. You can see the outline of her bush underneath.
Heat rises to your face. You look to see if your wife, Andrea, has noticed. She hasn’t. Your wife is getting dressed and listing things for you to do when you get home.