With the way that O. Henry writes, there are always examples of things like this in his stories. Let me list a few.
Early on in the story, when Gillian is talking to Old Bryson, he mentions that he has been to the offices of his "legal corsairs." This is a metaphor in which he compares lawyers to pirates.
A little bit later, the author describes the amount of interest that Old Bryson has in Gillian's story. Old Bryson is described as
showing as much interest as a bee shows in a vinegar cruet
This is a comparison that is done directly, using the word "as." Therefore, it is a simile.