The Treasure Hunt (CD, Unabridged edition)

Montalbano opened the door to step out. But Gallo held him back, putting one hand on his arm. What's in there, Chief? If it's what I think, it's something so horrific that it'll haunt your dreams for the rest of your life. When a crazed elderly man and his sister begin firing bullets from their balcony down onto the Vigata street below, Inspector Montalbano finds himself a reluctant television hero. A few days later, when a letter arrives containing a mysterious riddle, the Inspector becomes drawn into a perplexing treasure hunt set by an anonymous challenger.