The story "Just Lather, That's All" heavily relies on irony in order to tell the story and create the impression we get at the end.

Irony can be described as an event that is contrary to what we expect.

As mentioned in the other answer, we primarily see irony used at the very end of the story. The story centers around the Barber's conflict and his thoughts as he considers what would happen if he killed Captain Torres.

Throughout the story, we aren't sure if the Barber will complete the shave perfectly or kill the captain.

What we don't expect is to find out that Captain Torres had gone to the barber in order to see if he would be killed. It's unexpected for the reader and is ironic because it makes many of the Barber's thoughts no longer relevant.

In this short story we meet a Barber who is also a secret revolutionary. His enemy comes in for a shave and through this first person narration from the Barber, we find out about Captain Torres, who has killed and tortured many of the revolutionaries. The Barber shaves Torres as he contemplates cutting his throat while he is in the barber's chair, but he cannot go through with it. However, ironically, the shave actually rejuvenates Torres and makes him even look younger, rather than harm him.The most important irony of all, however, comes at the end of the story when Torres leaves unharmed and tells the Barber that everyone had thought that the Barber would kill him, but murder is a difficult task. Thus, the irony lies in the fact that all along the Captain knew the Barber wished to kill him and knew he was a revolutionary. Irony is responsible for the twist at the end which makes this a good story!