One of Thornton Wilder's most famous acquaintances was Sigmund Freud. Allusions to Freud or psychoanalytical concepts can be found in Wilder's plays and novels up to the end of his career. Perhaps the work most indebted to Freud's theorizing about the human psyche and behavior is the little-known one-act play The Rivers Under the Earth, first published in The Collected Short Plays of Thornton Wilder, Volume One, in 1997. The play depicts Wilder's typical nuclear family: a middle-class husband and wife with their teenage son and daughter. But in this play, Wilder goes beyond hints of the Oedipus and Electra complexes that appear in his more famous works to show his understanding of Freud's theory of the unconscious processes of the mind. During one night of the family's annual summer vacation, the parents realize the childhood events responsible for particular quirks of their son's and daughter's personality and actions. Thus, Wilder demonstrates what Freud called condensation and displacement, mental operations in which powerful repressed emotional experiences are associated with sensory phenomena or abstractions of them. Although scholars such as David Castronovo have noted Freudian influences in the one-act plays Wilder wrote in the late 1950s and early 1960s that were intended to be part of two seven-play cycles, The Seven Deadly Sins and The Seven Ages of Man, this article gives a more in-depth and technical reading of Wilder's dramatization of Freud's psychoanalytic theory of human behavior in the one-act play written during this same period.