Using reward money from the discovery of Vikram Szpirglas' pirate base, Matt Cruse is attending the Airship Academy in Paris.

While travelling through a storm in the Indian Ocean, his training vessel is caught in a vertical draft revealing a large airship drifting at 20,000 feet.

Upon returning to Paris, Matt meets with Kate de Vries, his friend and object of affection, to discuss the Hyperion's billionaire owner Theodore Grunel.

Kate announces that she plans to find "Grunel's treasure" using co-ordinates that Matt remembers in a special ship called a Skybreaker that will allow them to reach high altitudes safely.

Matt escapes with a gypsy girl named Nadira who claims to have a key that works on the Hyperion and proposes her own plan to find it.

They find small pieces of taxidermy, which Kate carries back to the Sagarmatha, as well as some larger ones including the intact body of a yeti.

In a room called the engineerium, they find a large key-activated machine that produces heat and a glass chamber housing the limp bodies of four aerozoans.

With Hal consumed by his lust for gold, the others read Grunel's diary and see frequent mention of a powerful enemy named "B".

The four climb out of the hatch but its connection to the Sagarmatha breaks under the wind and they are forced to spend the night on the Hyperion while low on food and oxygen reserves.

That night, the travellers learn that the machine they are using for heat is "Grunel's treasure"; a fuel cell capable of producing vast amounts of hydrium rather than gold.

Leaving Hal to tend to Nadira, who is suffering from altitude sickness, Matt sneaks into the engineerium and sees that the floorboards are concealing a fortune in gold bullion.