It was supposed to be a vacation with you and your wife and your best friend and his wife. But then they separated a week before the trip. Your friend was acting depressed, so your wife convinced him it would be good for him to come on the trip even without his wife. But after a couple of days, it was clear that he was feeling like a “third wheel”, hanging out with you and your wife. So your wife – in her typically very thoughtful way – suggested you two do something to make him feel better. That night you went back to your room right after dinner, while your wife stayed with him. The next morning she moved her things into his room, and for the rest of the week she acted as if she were married to him.
An unbelievable night was getting even better!