It's Christmas at the North Yorkshire Moors Railway, and cameras follow staff as they prepare for the festive season. In an effort to generate more winter revenue, a brand-new train, the Northern Lights Express, has been brought in, which features 25,000 lights fixed to a moving steam train. However, the staff are faced with a multitude of problems as generators break down, computers fail, and the engine that is pulling the new service develops a last-minute fault that threatens to stop the whole show in its tracks