L'histoire est tirée d'une pièce qui avait eu du succès à Londres. Il s'agit d'un officier de l'armée anglaise pendant la Première guerre mondiale. À la faveur d'une permission à Paris, il a une liaison avec une danseuse, puis il retourne au front. Là-bas , il est victime d'un choc...il perd la mémoire. Il retourne en Angleterre et il épouse une femme de la haute société. Ensuite réapparaît la danseuse avec un enfant. Conflit...L'histoire se termine par la mort de la danseuse.
A scholarly dissertation on the appearances of demons and witches in primitive and medieval culture, a number of photographs of statuary, paintings, and woodcuts are used as demonstrative pieces. In addition, several large scale models are employed to demonstrate medieval concepts of the structure of the solar system and the commonly accepted depiction of Hell.
As Francis (Friedrich Feher) sits on a bench with an older man who complains that spirits have driven him away from his family and home, a dazed woman named Jane (Lil Dagover) passes them. Francis explains she is his "fiancée" and that they have suffered a great ordeal. Most of the rest of the film is a flashback of Francis' story, which takes place in Holstenwall, a shadowy village of twisted buildings and spiraling streets. Francis and his friend Alan (Hans Heinrich von Twardowski), who are good-naturedly competing for Jane's affections, plan to visit the town fair. Meanwhile, a mysterious man named Dr. Caligari (Werner Krauss) seeks a permit from the rude town clerk to present a spectacle at the fair, which features a somnambulist named Cesare (Conrad Veidt). The clerk mocks and berates Dr. Caligari, but ultimately approves the permit. That night, the clerk is found stabbed to death in his bed.
The film follows two juxtaposed families: the Northern Stonemans—abolitionist Congressman Austin Stoneman, based on the Reconstruction-era Congressman Thaddeus Stevens, his two sons and his daughter Elsie—and the Southern Camerons, a family including two daughters, Margaret and Flora, and three sons, most notably Ben.