The 41st of Mary Pope Osborne's popular Magic Tree House series
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.