Stafford realizes that running on a battery and being a quiet engine is actually really useful.
The Lost Puff - Paxton persuades Thomas to wobble over a bumpy track for fun, and Thomas accidentally backs into Toby at the water tower and gets his firebox wet. When Paxton overhears Toby saying that Thomas has lost his puff, Paxton misunderstands and heads off across the Island of Sodor to look for it. Steamie Stafford - Stafford doesn't run on coal and water like the steam engines, he runs on a battery which is very quiet. So when Stafford overhears some children saying he doesn't sound like a proper engine, he becomes upset. Stafford asks Thomas and Percy to teach him how to make the same chuffing sounds they do. When he is sent to collect some lambs, his new noisy sounds make the lambs run away! Stafford soon realizes that being a quiet engine is actually Really Useful.