"The Magic Tree House: Moonlight on the Magic Flute" by Mary Pope Osborne - Jack and Annie head to 18th-century Austria, where they must find and help a musician by the name of Mozart. Decked out in the craziest outfits they've ever worn--including a wig for Jack and a giant hoopskirt for Annie --the two siblings search an entire palace to no avail. Their hunt is further hampered by the appearance of a mischievous little boy who is determined to follow them everywhere.
