It's Christmas Eve on the Island of Sodor and people are hurrying home to be with their families. It is snowing and Oliver, Duck, and Thomas are all out plowing the lines. Thomas is looking forward to Christmas, because no trains run that day, and the engines all get to stay in their warm sheds without their snowplows.
Meanwhile, Connor is on the Mainland collecting passengers who are returning home for the holidays. Unfortunately, Connor's train is soon full and some passengers are left at the station, including a little boy with crutches, who is worried. Connor promises that he will come back for them as there's still one more train before Christmas.
By the time Connor reaches Knapford, it is getting very late. Connor tells the Fat Controller that if he has more coaches, he will still be able to get everyone home for Christmas. He is concerned because more heavy snow is on the way. Connor assures him that he is a very fast engine and won't get caught in the snowfall.
Connor heads into the sidings, looking for more coaches. Suddenly, he hears a chorus of voices calling out to him. Connor does not know where the voices are coming from, but Thomas does. Thomas reverses into the siding and nudges a snowdrift. Snow falls to the ground revealing Duck's old slip coaches. Thomas explains that the slip coaches will be ideal because Connor can uncouple them without even having to stop.
Connor steams back across the island with the 3 slip coaches. Heavy snow starts to fall over Sodor which causes trouble for the engines. Paxton even manages to get stuck. This is enough for the Fat Controller to take action. He goes out onto the platform at Knapford to make an announcement to his engines. He tells them all that there can be no more trains and that the last train for Christmas will have to be cancelled. Percy is upset that so many people will not be able to get home to spend Christmas with their families. The Fat Controller spots a family stood lovingly together on the platform and has a sudden change of heart. He tells the engines that if they work together as a team, they have a good chance of clearing the line for the last train.
All of the engines get to work. Thomas and Percy clear the line to Wellsworth. As they stop outside the station, Percy spots some lights in the sky. Percy believes it to be Santa Claus, but it turns out to be Harold who is on duty looking for anyone stranded in the heavy snow.
Edward and Henry busily clear the tracks beyond Maron, but it's Emily who has the hardest job of all; clearing the tracks from Vicarstown to the Mainland where the snow is deepest of all. She is quickly running out of steam and is about to give up when she hears a loud whistle. It's Hiro coming from the opposite direction. He has no trouble charging his way through the snowdrifts. Hiro then spots something in the sky and thinks it might be Santa, but it is only Harold once again.
Connor drops the first slip coach off at Kellsthorpe Road Station, then the second at Maron, and then the third and final one at Wellsworth. Unfortunately, Connor uncouples the last coach too close to the station and it doesn't stop. If it is not pushed back to the platform, the passengers will be left stranded in the snow. Luckily, Thomas is there and is able to shunt the coach back to the platform.
When Connor finally arrives at Knapford, the little boy with crutches he met earlier that evening thanks him for getting them all home for Christmas. Then, the Fat Controller arrives and thanks Connor for all his hard work and determination. Connor says that his efforts would've been in vain if it hadn't been for his friends helping out. The Fat Controller thanks all the engine for their help and leaves. The engines leave, too, except for Thomas who spots Harold again. Thomas calls up to wish him a "Merry Christmas" and reverses away. However, this time it isn't Harold, it's the real Santa!