La historia comienza con el narrador que se hace llamar William Wilson, denunciando su pasado derrochador, aunque éste no se siente culpable, pues entiende que ningún otro hombre ha sido tentado de igual manera antes. Narra la infancia y juventud de William en un colegio isabelino. Relata que allí conoció a otro chico con su mismo nombre, parecido a él y nacido el mismo día, el 19 de enero, fecha de cumpleaños del mismo autor. Compite con este muchacho, pero él le supera fácilmente, de manera que lo considera prueba de su auténtica superioridad. Este chico comienza a imitar la forma de vestir, la manera de andar e incluso la forma de hablar del protagonista (aunque tiene un defecto en el habla que solo le permite hablar susurrando), y llega un momento en que William descubre que éste tiene exactamente su misma cara. Al ver esto, William abandona inmediatamente la academia, sólo para descubrir que su doble se ha marchado el mismo día. William con el tiempo estudia en Eton y Oxford, haciéndose cada vez más depravado y ganando enormes cantidades de dinero mediante engaños al jugar a las cartas con un pobre noble y la seducción de una mujer casada. En esta etapa aparece su doble de nuevo, con la cara siempre cubierta, susurrando unas pocas palabras que alertan a otros sobre el comportamiento de William. En el último de estos incidentes, en un baile en Roma, William arrastra a su doble a una antecámara y lo apuñala. Tras la acción de William, aparece un enorme espejo en el que éste ve el rostro del fallecido, momento en el que el narrador siente que está pronunciando las palabras: en mí existías, y en mi muerte, ve cuán profundamente te has asesinado a ti mismo. The story follows a man of "a noble descent" who calls himself William Wilson because, although denouncing his profligate past, he does not accept blame[dubious - discuss]for his actions, saying that "man was never thus [...] tempted before". After several paragraphs, the narration then segues into a description of Wilson's boyhood, which was spent in a school "in a misty-looking village of England". William meets another boy in his school who shared the same name, who had roughly the same appearance, and who was even born on exactly the same date (January 19, Poe's own birthday). William's name (he asserts that his actual name is only similar to "William Wilson") embarrasses him because it sounds "plebeian" or common, and he is irked that he must hear the name twice as much on account of the other William. The boy also dresses like William, walks like him, and even looks like him, but he could only speak in a whisper, he imitates that whisper exactly. He begins to give orders to William of an unspecified nature, which he refuses to obey, resenting the boy's "arrogance". One night he stole into the other William's bedroom and saw that the boy's face had suddenly become different. Upon seeing this, William left the academy immediately in horror, and in the same week, the other boy followed him. William eventually attends Eton and Oxford, gradually becoming more debauched and performing what he terms "mischief". For example, he stole from a man by cheating at cards. The other William appeared, his face covered, whispered a few words sufficient to alert others to William's behavior, and leaves with no others seeing his face. In his latest caper, he tries to seduce a married woman but the other William stops him at a ball in Rome; the enraged William drags his "unresisting" double-who was wearing identical clothes-into an antechamber, and stabs him fatally. After William does this, a large mirror suddenly seems to appear. Reflected at him, he sees "mine own image, but with features all pale and dabbled in blood": apparently the dead double, "but he spoke no longer in a whisper". The narrator feels as if he is pronouncing the words: "In me didst thou exist-and in my death, see [...] how utterly thou hast murdered thyself."