A librarian was found dead behind the front desk. Next to her hand was a book opened to page 45, a pen, and a slip of paper with the numbers 4, 8, 15, 16, 23, 42. The prime suspect is the assistant librarian, whose name is Mark. Mark claims he was shelving books in the history section all evening. Detective Cole arrested Mark immediately. Why?
The library was closed on Sundays, or Mark referenced a detail only the killer knew.
Actually, look at the book page and numbers: The victim wrote a clue. Wait, the question implies Mark slipped up. If Mark claims he was shelving books, but the library had no books... No, let's look at standard riddle mechanics: Mark mentioned the specific book before police announced it, or the numbers spell something. Let's make it simpler: Mark claimed he saw the librarian reading a mystery novel, but the book open was a cookbook.
About this riddle
Detective riddles are tiny mysteries. Look for the detail in the story that does not fit; it is usually the clue that solves the case.
Difficulty: Easy. More like this: Detective riddles with answers or try Truth & Lie Island for a different kind of puzzle.
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