A man is sitting in a bar and starts talking to the barkeep.

"Say, you ever notice how there's vapor in the air?"

The barkeep just stares.

"You know what I'm talking about?" asks the man.

The barkeep says nothing.

"Hello? Do you hear me?" asks the man, waving his hand in front of the barkeep's face.

"There's nobody here," says the barkeep.

There was no barkeep.