Fifteen-year-old Peak Marcello is invited to climb Hkakabo Razi, one of the most isolated mountains in the world, but getting there involves a four-week trek through a tropical rainforest that is rife with hazards, which turns out to be more dangerous than summiting the mountain itself.

Geronimo follows clues in a diary all the way to Mouse Everest in search of his old friend Professor von Volt who has mysteriously disappeared.