Outside it was getting dark. The streetlight came on outside the window. The two men at the counter read the menu. From the other end of the counter Nick Adams watched them. He had been talking to George when they came in. (5)
Because Nick’s character is introduced as someone watching, observing, we know he is going to be affected by whatever happens in the story.
"Hey, bright boy," Max said to Nick. "You go around on the other side of the counter with your boy friend."
"What’s the idea?" Nick asked. (57-8)
Nick’s question is echoed twice in the following lines, but he establishes the general feel of innocence in the lunchroom. The three victims are so unaccustomed to such behavior, they can’t even figure out what’s going on.
"No," said Max. "It ain’t that. Bright boy is nice. He’s a nice boy. I like him." (122)
For being a killer, Max definitely has a more compassionate, emotionally innocent side to him.
Nick stood up. He had never had a towel in his mouth before. (145)
In his essay on The Killers, author Robert Penn Warren talks specifically about this line as evidence of Nick’s innocence. He points out that the word "towel" is used instead of "gag," making the experience more real and jarring – it may be something out of a movie, but it’s really happening to poor Nick.
"I was up at Henry’s," Nick said, "and two fellows came in and tied up me and the cook, and they said they were going to kill you."
It sounded silly when he said it. (175-6)
For Nick, there is still an element of absurdity to all this. Because of his innocence, he finds this sort of encounter with evil a bit fantastical.
"Isn’t there something I could do?"
"No. There ain’t anything to do."
"Maybe it was just a bluff." (187-9)
Nick’s eagerness to help is an indication of his innocence and inexperience; he’s never before been up against a situation like this, so he naively believes he can stop it.
"I wonder what he did?" Nick said.
"Double-crossed somebody. That’s what they kill them for." (228-9)
George speaks with all the authority of experience; though he’s likely never encountered a situation like this before, he’s accepted that these sorts of things do happen.
"I’m going to get out of this town," Nick said. (230)
This is arguably the most important line in The Killers; this is when we see that Nick has been deeply affected by the evening’s course of events. We understand that he has changed, and that part of that change has to do with losing innocence.