A dinosaur skeleton has been stolen from the museum. Since the other guy is apparently busy, the authorities go to 223 Baker Street and enlist the help of Hairlock Combs and his sidekick Gotsome. The thief keeps taunting them with notes that "the best bones go to Symphony Hall", but they start at the museum anyhow, disguising themselves as a pantomime horse. They build a mock skeleton out of scrap lumber, but discover it won't fit through the door or window. When Gotsome makes a musical noise sliding down the neck, they finally go to Symphony Hall, where the world's largest xylophone bears a strong resemblance to the skeleton. And just how *did* the skeleton get out? By answer, Combs pulls off a mask and reveals that he's the thief, not that it's a real answer.