In Percy's Promise, Percy braves a storm to keep his promis to get the children home from the beach. In Percy Takes the Plunge, Percy disobeys a danger sign and is pushed into the sea.

Attempting to hurry through his work so that he can give some school children a ride, Thomas the Tank Engine must overcome a series of obstacles.

While Thomas befriends the new steam engine Belle, Percy makes friends with the diesel engines at the dieselworks, and it causes tensions to flare in the town of Sodor.