Percy must deliver Santa's Christmas letters to Vicarstown urgently, but a sack of letters is left behind at Dryaw. Harold tries to take them to Percy, but the little engine only thinks he is only mocking his speed. After a snow heap blocks off a tunnel, Harold takes the mail to Vicarstown instead, but ends up getting stuck on the Mainland afterwards. Percy later finds him and decides to repay Harold for his good deed.
Writer: Helen Farrall