In "The Guest," the Arab has murdered his cousin. Though the details of this crime are sketchy, Balducci states that the Arab killed his cousin as a result of a "family squabble" in which one man owed some grain to the other. In the ensuing conflict, the Arab killed the man with a billhook, a tool that has a sickle-shaped blade.
While the story contains no formal admission of his guilt, the Arab does not deny the murder to Daru nor does he provide much information about his motivation. When asked why he did it, for instance, the Arab simply states:
"He ran away. I ran after him."
After hiding for one month, the Arab was arrested and this is how he came to be in the custody of Balducci and, later, of Daru.