Cousins Patrick and Beth travel in Mr. Whittaker's invention, the Imagination Station, to thirteenth-century China, where they meet Marco Polo and Kublai Khan and are mistaken for Christian shamans.

At the end of World War II, Wade is transported to a war-torn alternate world called Marus, where he finds himself a key figure in a political power struggle and unwittingly helps to bring the Unseen One's judgment on a corrupt people.