The annual Gala Festival is staged, showcasing steam engines from up and down the country. As part of the events, the North York Moors Railway has agreed to swap its precious 100-year-old Q6 engine, the last example in the world, with an engine from the Severn Valley heritage railway. However, there is a problem as the Q6 is undergoing a two-year overhaul and is not ready. A crack has been found in the engine box, and there is no specialist steam copper welder available at short notice to fix it. If the Q6 cannot be sent to the Severn Valley, the entire festival may be ruined