Thomas is excited because it is time for a winter party, but on his travels, he meets Percy on the Fenland Track. Percy is suffering from a cracked side rod, so Thomas kindly shunts him to the Steamworks. Shortly, Thomas finds Edward who is complaining about a "popped piston", so Thomas pushes him to the Steamworks too. A bit later, Thomas meets up with Stanley who has a faulty firebox. Thomas shunts him to the Steamworks as well.
Thomas is sure that his friends will be repaired in time for the children's winter party, but Victor isn't so sure. Edward, Percy, and Stanley are upset at the thought of missing the party, but Thomas has an idea: he wants to hold a party for them at the Steamworks. Thomas inadvertently makes his first mistake: he doesn't tell Victor his plan - because he looks too busy.
Thomas puffs away to make arrangements and soon finds Charlie at Maithwaite. Thomas decides that Charlie's jokes will be excellent for his friends' party and the pair puff back to the Steamworks. Once there, Thomas tells Charlie to quietly tell his jokes so that he doesn't bother Victor and Kevin. However, he isn't very good at being quiet and Victor soon hears him laughing and orders him and Thomas to leave. Thomas quickly reverses, but carelessly backs into and derails Charlie. Thomas sets off to find Rocky. At the docks, he spots Rocky loading Christmas trees onto a flatbed. Thomas explains his plan to Rocky and suggests that they could borrow one. Rocky thinks it's a good idea and Thomas tells him not to tell Victor about their plans as they set off.
Back at the Steamworks, Victor is still very busy whilst Rocky unloads the tree. Victor hears Rocky who drops the Christmas tree crate - right in front of Kevin who bashes into it. Victor is cross and Thomas decides that he'd better tell Victor his plan. Victor is very sympathetic and tells Thomas that he should have told him the plan earlier. Victor then agrees to help Thomas with the preparations and tells Kevin to make room for the Christmas tree. Soon the Steamworks is decorated with sparkly lights and it's time for the party to begin. Percy thinks it's the best party ever - and Thomas has to agree!