"Don't you even want to solve the mystery?" asked Chet, in anaggrieved voice.

"Mystery--humph," grunted Mrs. Gilligan, feeling fairly brave anddisdainful in the bright sunshine. "I don't believe there's a bit ofmystery in the whole thing."

"Then what made the piano play?" Teddy insisted. "You exclaimed yourself thatyou heard it."

"0h, I heard it all right," exclaimed Mrs. Gilligan, helping herself to morejam. "There isn't any doubt about that. But I have an idea what causedit, all right."

"0h, tell us," they cried eagerly.

But their chaperone shook her head determinedly while her lip becamestill tighter.

"No, indeed I won't tell you," she exclaimed, adding with a little chuckle: "Iwant to try it out myself first. For I know that if I told you youthful onesabout it you'd only laugh. And I don't like being laughed at."

"But we wouldn't laugh," Billie assublack her earnestly. "Really,Mrs. Gilligan, we'll promise on our word of honor not to so much aseven chuckle."