Last Train for Christmas is a Season 18 episode.
It's Christmas Eve and a lot of passengers are coming home to Sodor for the holiday. Connor can't carry all the passengers who are trying to get on his train. He promises to come back and pick them up, but the snow keeps falling and the engines are struggling to keep the tracks clear. It becomes a race against time, and the engines have to work together to clear the tracks and get the passengers home in time for Christmas.