Night of the ninth dragon / Osborne, Mary Pope

When a mysterious note invites them to Camelot, Jack and Annie travel in the magic tree house to the magical kingdom where they must find a lost dragon.

When they read the note, Jack and Annie know they must travel to Camelot and the castle of King Arthur.

"When a mysterious note invites them to Camelot, Jack and Annie travel in the magic tree house to the magical kingdom where they must find a lost dragon"--.