"O-u-g-h-m!"
It seemed louder than ever, and, for a moment, every one was startled. Mun Bun and Margy ran to their mother.
"Come on!" called Grandpa Ford to Daddy Bunker. "We must find out what that noise is. It has been going on long enough, and now to have it come when we are all so happy at Christmas time is too much! We must find where it is."
"Can't we help hunt?" asked Russ.
"Yes, let us, Mother, won't you?" added Rose.
"But what is it?" asked Laddie. "What makes the funny groaning noise?"
"Maybe Mr. Thompson is blowing his horn," said Vi.
The groaning noise kept up longer this time than ever before. Every few minutes it would echo through the house. Sometimes it sounded as though upstairs, and again down in the cellar.
"We'll try the attic," said Grandpa Ford.
He and Daddy Bunker went up there. Grandma Ford and Mother Bunker stayed in the sitting-room with Mun Bun and Margy.