A major theme of Lest Darkness Fall is that of the "castaway." The archetypal example of this theme is Daniel Defoe's Robinson Crusoe (1719), in which the main character is shipwrecked on an island far from civilization and must use his ingenuity to survive on his own. Padway is a "castaway" in sixthcentury Italy. Like Crusoe, he must find ways to feed, clothe, and house himself, and he must learn to cope with his strange new environment.
Throughout the novel, he uses his wits and common sense to survive the many surprises the ancient world has for a twentieth-century American.