is a 2004 science fiction young adult novel by Kenneth Oppel. It is set in an alternate universe where airships and hot air balloons have replaced airplanes as the primary mode of travel. The book has won several awards, including a Governor General's Award for children's literature, a Michael L. Printz Award honor, and a Bulletin of the Center for Children's Books Blue Ribbon award.
Matt Cruse is a cabin boy on the airship Aurora. One night while on watch, Matt spots a drifting hot air balloon that does not respond when the captain of the Aurora tries to raise it on the radio. Matt helps to rescue the injured pilot from the balloon. The man tells Matt about mysterious ghostly creatures that he saw in the sky, then he passes away.
The next day, a wealthy passenger named Kate de Vries boards the ship. Kate is the granddaughter of the balloon pilot and a talented airship engineer. She is on the airship to look for the creatures her grandfather described before his death. That night, Kate seeks Matt out and shares her grandfather’s notebooks with him.
Matt takes the notebooks back to his cabin and reads the account of the strange creatures. Kate’s grandfather describes them as a cross between a bat and a human. He also details some of the creatures’ unusual mating and feeding habits. Eventually, the creatures migrate on, which Matt notes occurred just five days before the Aurora picked up Kate’s grandfather. Matt is skeptical of the account, but Kate believes that the creatures are real and the Aurora intersects with their migration route.
In the navigation room, Matt checks the Aurora’s route to see when it will pass close to the coordinates described in the journal. He notices another airship approaching the Aurora and radios the captain. Despite the captain’s best efforts to evade them, the Aurora is caught and boarded by air pirates who take the passengers’ valuables. While leaving, the pirate ship rips a hole in the side of the Aurora, forcing it down on an uncharted island.
Kate recognizes the island from her grandfather’s journals and sets out to explore it. Matt feels obligated to go with her to protect her, because all Kate can think of is finding a skeleton of one of the strange creatures so that she can prove her grandfather was not delusional. The two find one of the skeletons, and Kate insists on coming back later to collect the bones properly.
When Kate and Matt return to the Aurora, they learn that repairs are going well and the ship will be able to lift off soon. Kate plans to retrieve the skeleton early the next morning. She and Matt document the bones, but before they can return to the ship they are trapped by a severe storm. When they finally get back to the Aurora, they find it damaged beyond repair. However, Matt tells the captain that he found the material they need to repair the ship while he was looking for the bones.
A second round of repairs to the ship begins. Kate’s guardian, Margery, confines her to her room to keep her from going back into the jungle, and Matt refuses to help her escape. Kate sneaks out on her own and goes back to the site of the bones where she finds a nest used by the creatures. Matt and the rest of the search party arrive in time to see one of the creatures land in the nest.
Kate is now determined to get a photo of the creature before she leaves. She tries to lure the creature with a fish, but the smell sends it into a frenzy. It chases Kate and Matt before Matt is able to frighten it away. He and Kate flee the area, and she is forced to leave her camera behind. While coming out of the jungle, they are intercepted by the pirates from earlier who use the island as a base. The pirates fortunately do not recognize Matt and Kate, giving them the opportunity to escape once more and warn the Aurora.
When they reach the Aurora, they find that it is already under the control of the pirates. They contrive to drug them with a sedative which puts most of the pirates to sleep. Matt and Kate sneak around the ship to deal with the rest of the pirates. Matt and the pirate captain confront each other on the exterior of the ship, and a flock of creatures arrives to kill the pirate. Matt rushes to the control room and takes control of the Aurora.
Matt receives a reward for helping to capture the pirates and uses the money to attend university with Kate. She convinces him to return to the island with her to conduct additional research on the creatures.