Who is banging on the door in the middle of the night? Barney, Roger, Diana and Snubby investigate and find tracks in the snow, but there is no one to be seen.

Mrs. Tickle says it's a warning, last heard at Rat-a-Tat House a hundred years ago. Can it have something to do with the snowman which see is positive she saw watching her through the kitchen window?

The four friends are determined to solve the puzzle, but when Snubby turns detective, he mysteriously disappears...