Will, have you been paying attention to the number of times we had to go one...

Will, have you been paying attention to the number of times we had to go one passage farther than the first left?"
"I've been trying to. Why?"
"This place is really getting to me. I don't like the idea of spending the rest of my life down here."
Will sighed. "Relax, Sarah. Just lie down and go to sleep."
"Humor me and tell me how many times."
"Okay. Three. We've hit three dead ends."
"It's four, Will."
"I knew that. I was just checking to see if you were on your toes.