CGI animation. Ernie, controller of International Underground, is always on hand to help his friends and to get passengers to their destinations safely. He is helped by trains Victoria, Bakerloo, Circle, Jubilee, the twins Hammersmith and City and Ernie's friends Millie and Mr Rails. Victoria fears she is going to be replaced by a newer, faster train when she overhears Ernie talking to Mr Rails. Jubilee wants to prove that he is the fastest on the track but comes unstuck when he blows a gasket.