There were two fifty pence pieces in the money Colin's mother gave him for her Christmas shopping - but the strange thing was, they didn't weigh the same. This discovery sets the Secret Seven on the trail of a sinister forgery racket. Surely all the Father Christmasses in town can't be involved? The Seven waste no time in trying to trace the source, but will tracks in the snow lead them to the unknown forgers in time, or will the forgers find them first?