A shot in the night at the Château of Ambrumésy. A secretary lies dead, a burglar vanishes from a walled park that no one could have left, and four priceless Rubens paintings turn out to have been replaced by copies. Only one clue remains: a scrap of paper covered in dots, numbers, and strange signs. <p/>Arsène Lupin, gentleman-burglar, has been wounded, and he has disappeared. <p/>Into this mystery walks Isidore Beautrelet, a seventeen-year-old schoolboy on his Easter holidays. He outwits the examining magistrate, humiliates the police, and sets out to solve a cipher that has guarded a royal secret for centuries. The trail runs from Julius Caesar to the Man in the Iron Mask and from Marie Antoinette to the chalk cliffs of Étretat. There Beautrelet faces the most brilliant adversary of his life in a duel of wits between the boy detective and the master thief. <p/>
