There is a mystery in books, but sometimes there could be mystery in selling books too. You may wonder what could be mysterious in that, but soon you will see that the book market can be rather tricky, especially the black market...
Detective Mary stands before another interesting case. She is looking after the mysterious bookseller who works on the black market. Specific about him is that he offers on the black market very rare editions of books and sells them at seriously high prices. The question is who is this man and how did he manage to find those rare editions? Also, no one knows how does the bookseller look like so his identity is completely hidden.
You can realize that detective Mary has a difficult case this time. She starts from zero, so she has to have in mind all the circumstances around this case, in order to get to some trace that will help her for the case. Let's act like real detectives and help Mary find some piece of evidence that will make her job easier.