The story begins with William McGarthy, a young Texan struck by wanderlust, who decides to sell his possessions to fund a global adventure. His journey starts with thorough explorations within the United States before setting off for Sydney, Australia. During a ship stop at Samoa, McGarthy ignores warnings about the dangerous locals and wanders into the forest. While he relaxes, unaware of the danger, his fellow passengers are attacked by head-hunters, and McGarthy is left behind.

Knocked unconscious by an unknown assailant, McGarthy awakes in a native hut, weak and disoriented but unbound. He receives food from a native who ominously hints at McGarthy being fattened for a cannibalistic feast. Realizing his peril, McGarthy manages to escape after a violent encounter with his captor. He flees into the jungle, pursued by head-hunters, and eventually finds refuge with a peaceful tribe of Malay descent, far from the coast and cannibals.

McGarthy spends twenty years with the tribe, attempting to return to the coast several times but always thwarted by the cannibals. His isolation ends with the sudden arrival of an airship, to which he desperately signals for rescue. The airship's crew, transporting goods from Australia to England, informs him that it is now 1940 – he has been gone for two decades. Returning to a radically transformed world, McGarthy learns of wars that have reshaped borders and politics, including conflicts involving America, England, Japan, and others.

Technological advances such as personal flyers, electric cooking, and automated homes astonish him. When he finally reaches his sister's home, he is reunited with family but continues to grapple with the new realities, including drastic changes like the prohibition of tobacco and coffee in the United States.