It all started with a comment from a friend about my sister's ass. Without thinking I've told him: "Yes, she has a nice ass, I've been there already". Only after I realized I've told him too much. The guy jumped from his chair and asked me if I was joking. I told him yes, I was joking but only then I understood his real intentions. He was about to offer me money if I could prove what I've said was true. I told I could prove it, it only depended on how much he wanted to pay...