Burroughs imagines a future two centuries onward in which that view prevailed and the western hemisphere severed contact with the rest of the world.

Consequently, the eastern hemisphere has exhausted itself in war and Europe descended into barbarism while the Americas, sheltered from the destruction, have continued to advance and joined peacefully into the union of Pan-America.

In 2137, Pan-American Navy Lieutenant Jefferson Turck is commander of the aero-submarine Coldwater, tasked with patrolling the 30th meridian from Iceland to the Azores.

It is implied that the perfidy of the Coldwater’s second officer is behind its misfortunes, as well as the abandonment at sea of Turck and three crewmen in a small boat while attempting repairs.

Turck falls into the hands of raiders from the Abyssinian Empire, a black super-state ruling all of Africa, most of Europe, and the Arabian peninsula.

While the Abyssinians' technology is roughly equivalent to that of the nineteenth century, the white savages that populate Europe in Turck’s time are no match for them.

Turck watches powerless as white slave women are offered to the emperor for his harem, including the heroine Victory, queen of the primitives of England.

Communications between the hemispheres are re-opened, with commerce to follow, and Turck, despite violating the edict against crossing the 30th meridian, is hailed as a hero in Pan-America.

Jefferson Scott, Jr. and Robert Gordon, hunters in the Belgian Congo, are thrown together with missionaries Sangamon and Mary Morton and their daughter Ruth.

Ruth attempts to prove her marriage to Virginia's father by writing to Robert Gordon, who witnessed the ceremony, but he is now deceased.

Moved but unable to provide the desired proof, Gordon writes back of his intention to sail to Africa to seek documentation of the marriage there.

Realizing his omission, Gordon visits the Scott home to deliver the envelope to Virginia and Ruth, unaware that Taylor and Kelley have returned from Africa and still plan to kill him.