I can't cancel his booking without being severely penalized by Airbnb. (Later, I found out I could have contacted Airbnb's host support and they would have cancelled it without a penalty since he broke the guidelines, but at the time I did not know that.)
His daughter turned out to be someone who (I am really trying to be polite here since this is a public forum) should not be living on her own. She was not...OK. After one really crazy incident, the next morning, I called her dad on the phone and explained the situation. They agreed to cut the booking short, and I ended up having to refund them their "unused" nights.
I straight up asked him, as politely as I could, "I don't mean to pry...but what's going on with your daughter?" His reply: "Well, she's never been diagnosed with anything..."
If I wouldn't have already had other people booked on the Airbnb for later dates, I would have taken down the listing after that experience. It was a nightmare. My roommate had to clean up the room, and that was a nightmare too. We were all pretty over it at that point.