The narrator introduces himself with a fake name, William Wilson.
He begins his story and explains that, as a child, he is prone to imagination and ungovernable passions, and largely left to his own devices.
He recalls his schoolboy days and explains that he maintains superiority over all the other boys except for one, another William Wilson who looks just like him and was born on the same day.
The narrator explains the nature of their relationship: part competition, part affection.
This relationship quickly sours, however, as William grows to hate his double.
One night he creeps over the sleeping figure of his double. He is so horrified by their similarities that he flees school.
William goes to Eton, but is tormented by his double there as well.
He then goes to Oxford and indulges in endless vice, in particular gambling. One night, when he has just won a huge sum of money by cheating, the second Wilson shows up and outs him.
William flees all around the world but can never shake his double.
One night, when he is about to start an affair with a married woman, Wilson shows up yet again. William drags his double to a room and stabs him with his sword, only to find that he has stabbed his own reflection. The double informs Wilson that he only lived through his double, and that now Wilson has murdered himself.