Mortimer is a young bird... who can't fly. His wings just aren't big enough, not yet, but that doesn't stop his well-intentioned parents from making him jump off the tree branch, again and again and again. It's terrifying and painful for Mortimer-but he keeps trying. Then, one night, he overhears his parents talking, and discovers that they suspect he's a lazy bird! Mortified, Mortimer decides to run away from the nest. He won't return until he has learned how to fly. Mortimer's journey takes him to a place he has never seen or heard of before: The City! There, he discovers strange metal creatures ards) and strange gangly creatures (humans)-and meets the most talkative worm who has ever lived -Lucius! Mortimer also happens to be a vegetarian, so the two strike up an almost immediate friendship. It's not soon before Lucius hatches a plan that will allow Mortimer to visit Wormland-a plan that involves a human sock and the invention of the largest worm who has ever existed!