Percy's Promise is the second episode ever made in Season 3.
Thomas is busy and asks Percy to take the children home from Sunday School. Percy accepts, but when he leaves, the weather turns bad and it begins raining. Percy battles onward, but has to pass through a flooded field and his fire goes out. The crew chop up floorboards from the brakevan, and Harold thoughtfully drops hot drinks for them - unluckily landing on Percy's boiler. Percy makes it home safely and is lauded by Thomas and his passengers.
- At the beginning of the episode, Thomas is on Toby's old tramway.