Why would anyone need to weigh or measure a huge green dragon? Ben finds out when his new friend Mortimer, a huge green dragon tells him he can't fly. He is heartbroken; all dragons should fly, shouldn't they? He dreams of adventures with his father in wild, wonderful places, and Ben is desperate to help make that dream come true.

The task is enormous, and Ben can't do it alone. Luckily, the whole village pitches in: the quarry workers, the primary school children, the firemen, the hilariously hopeless Knit and Natter Group, the mountain rescue team and even the steam engine company. Everyone in the village is happy to help Mortimer achieve his dream.

With clever ideas, hard work, and the help of the professor Ben sets out on an unforgettable mission that will test his courage, creativity and friendship in ways he never expected.