Pearl Petal and her friend Ben have the great honor of being the mysterious Dr. Woo's apprentices for the summer. With their families thinking that they are working at a worm hospital, they are really helping Dr. Woo with imaginary creatures! The kids meet leprechauns, a sasquatch, fairies, and more and are excited at the opportunity to discover what other kinds of creatures are out there.
When Petal discovers a monster in the lake behind the hospital, she wants to get a closer look. But when she and Ben get close, Ben is captured by the creature and held hostage on an island in the middle of the lake. It's up to Pearl to rescue Ben!
