Three weeks after our honeymoon, we spent our first Friday night staying at home, too tired to go out. My new wife Ally and I sat up in bed, scrolling through our phones. We were just about ready to turn off the light and make love. Her phone chimed as a new text arrived from her older sister Lexy, and Ally proclaimed, "Oh, my God, Lexy is such a slut!" "Why, what's she up to now?" I asked, intrigued. "She must have sent...