While spending Christmas in 1939 with a well-meaning aunt, a young boy who does not believe in Santa Claus has an unusual experience that changes his thinking.
When Santa Claus comes down with a terrible cold just before Christmas, his animal friends send him to bed, finish all of the presents, and load the sleigh, hoping that he will be well in time to make his deliveries.
Santa Claus changes many things about himself, including his diet, clothes, and means of transportation, in an attempt to become a new, improved Santa.
On Christmas Eve, McDuff's persistent "woofing" begins to annoy Fred and Lucy, but it leads to the rescue of Santa, whose sleigh has gotten stuck in the snow.