Deep in the heart of children's imagination lies the land of Chuggington, where trains have come to life and everything runs on rails. The 'Chuggers' in this magical world are all based on modern engines of every kind, from stream-lined diesel locomotives and electric bullet trains to trolleys and old steam engines. Three apprentice engines (called 'trainees' of course!) are learning to ride the rails and perform essential tasks - Wilson (an eager but slightly impetuous red engine), Brewster (a loyal and rugged freight engine) and Koko (whose speed and daring deeds sometimes get her into mischief).

The trainees have much to learn from their instructor, Dunbar, in the training yard of the Chuggington depot. When they finally master skills like carrying passengers smoothly or operating the loading doors of a quarry car, the trainees earn the chance to perform tasks outside the depot. Vee, the organised announcer with speakers all over Chuggington, reveals each Chugger's mission on her dispatch board - including which of the four coloured tunnels they will take to get to the vast Chuggington landscape beyond.

On their adventures, the trainees learn valuable lessons about helping friends, following instructions, keeping promises, and perhaps most of all, enjoying a sense of wonderment about the world. Every Chugger has something to learn, and sometimes it's the older and more experienced ones who must learn from the youngsters!