In one corner, a ladder has been left standing in front of one of the bookcases. Could it be? You don’t suppose Penelope would go to all that trouble to shelve a special book up high—and then leave the ladder just standing there in a telltale location, do you?
    But, knowing her, you conclude that’s exactly what she might have done. If you’re lucky, nobody else has moved it since. The public hasn’t been around. It’s certainly been your lucky day so far. You climb the ladder.
    On the top shelf lie twelve black books with gold and peach-colored trim. One by one you examine them. The eighth in line appears slightly different. … Eureka! It is not a book but a hollow leather case fashioned from the original book cover and secured by a gold band that extends from the front around the false-pressed pages to the back.
    Embedded in the band are three recessed squares with black digits and tiny dials. At present it is set to 000. When you turn the dials to 594, the book pops open. Inside are a letter and some typewritten sheets. You start to remove them when you hear a gasp.
    Standing below is Penelope.
    “I was just instructed to fetch that for you, but I see you’ve found it—and opened it as well! My, but you are clever. I’d forgotten where the book was and the combination I’d used.”
    “This is our lucky day,” you tell her.
    “Oh, that reminds me … there was also a disc of some kind for you. But I … uh, sorry … accidentally posted it to The Royal Society, which was where it was supposed to go next. And those other papers—now where did I put them?”
    You pull the typed sheets from the case. “These?”     “Yes, yes! Oh, terribly sorry about all my dreadful mistakes. Thank goodness you’re so resourceful. … Right. I’m off to practice for tonight’s show. I’m better at that sort of thing, you’ll see.”
    Penelope, embarrassed, leaves in a hurry. Anxious to read Uncle Arthur’s letter, you climb down and settle into one of the big leather chairs. The door opens and Christopher walks in, asking if the receptionist found you. You tell him you discovered and unlocked the case.
    “Good that I did, because she’d completely forgotten.”
    The two of you high-five—another puzzle solved.
    Uncle Artie’s letter runs to several pages. As soon as you begin, you realize that at long last, this is going to explain everything.