Each day, the big trucks go to work. They scoop and hoist and push. But when Digger discovers something growing in the rubble, he sets in motion a series of events that will change him, and the city, forever.

Digger and his friends meet a hungry caterpillar who chooses Digger as its safe place to make a cocoon, making Digger cease his work to care for the small creature who surprises him and his friends.