[1] Heir to the Austro-Hungarian throne in hiding Prince Aleksander, and Scottish midshipman Deryn "Dylan" Sharp rescue Serbian inventor Nikola Tesla from the site of a 1908 Siberian Tunguska event meteorite blast.

Along the way, Alek sees through Deryn's male disguise of Dylan on the organic airship Leviathan while gradually learning of Tesla's motives of using his invented weapon Goliath to end the war on his own.

[2] As the airship Leviathan travels over Russia, Aleksandar, Deryn, and Newkirk are in the middy's mess with the perspicacious loris Bovril, talking about great circle routes.

Count Volger tries to expose her gender unless she discloses the imperial message, but drops the attempt after some convincing from Deryn, who dares not to shake the confidence of Alek, who admires 'Dylan' unaware of her masquerade as a boy.

The imperial message is to pick up a crate from the back of a fighting bear, but it is much heavier than expected, overloaded by metal parts and tools, and drags Deryn and Newkirk down into the trees until the crew manages to compensate by dumping clart (waste water) and other supplies.

Flying over Tunguska, Siberia, they notice the area has been destroyed, trees have been flattened and point in one direction, and many stripped corpses are present, including that of another organic airship.

By dropping dried beef at a distance to distract giant starving fighting bears, they rescue Nikola Tesla, his Russian soldiers and airship crew, who are holed up near the center of the destruction.

Alek decides to support Tesla in his mission to end the war with his magnetic beam, the Goliath, but sadly misses Deryn; who meanwhile is angry of his dismissal of her just because she is a girl.

In Tokyo, Tesla demonstrates the Goliath publicly at a conference in the Imperial Hotel, claiming the sky color will change in London.

At the Serbian consulate, Lilit (who has been made the assistant to the newly founded Ottoman Republic's ambassador since the events of Behemoth) reappears and tells Deryn about a German water-walker coming to attack Goliath, so Dr. Barlow convinces Captain Hobbes to keep watch.

When the Leviathan sees approaching bubbles underwater, they bomb the escorts, while they leave the largest to land to prove the attack and encourage the Americans to join the war, so she sends a warning by eagle to Alek.

Tesla hosts a dinner at his tower, hoping to do a demonstration that the Goliath can change the color of the Berlin sky, but under attack decides to fire for real, despite danger to the nearby Leviathan.

Dr. Barlow receives a message that tells her that the sample Deryn stole from under Tesla's bed was from a meteorite, proving Goliath did not cause the Tunguska event.

Alek relinquished his royal title as prince, with his only comment being a phrase associated with the Habsburgs: Bella gerant alii, tu felix Austria, nube or "Let others wage war.