"Is it why does a door swing?" asked Violet. "'Cause if it is, I can answer that one. I've heard it before. A door swings because it isn't a hammock."
"Nope! 'Tisn't that," said Laddie. "This is my new riddle. What goes through a door, but never comes into the room?"
"Say it again," begged Russ, who had not been listening carefully.
"What goes through the door, but never comes into the room?" asked Laddie again. "It's a good riddle, and I made it up all myself."
"Does it go out of the room if it doesn't come in?" asked Rose.
"Nope," answered Laddie, shaking his head. "It doesn't do anything. It just goes through the door, but it doesn't come in or go out."
"Nothing can do that," declared Russ. "If a thing goes through the door it's got to come in or go out, else it doesn't go through."
"Oh, yes, it does," said Laddie. "Do you give up?"
"Is it a cat?" asked Vi.
"Nope."