Air date: February 25th, 1992 (UK), November 29th, 1991 (US)
Adapted from: Percy the Small Engine, "Percy's Promise"
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, the passengers and the Fat Controller.
Tropes featured in the episode:
- Alliterative Title: Percy's Promise.
- Big Storm Episode: A rainstorm hits Sodor as Percy is tasked with taking the children from the Vicar's Sunday School home. A section of track gets flooded, and Percy has to travel through it, which becomes difficult when it puts out his fire.
- Bookends: At the beginning, Thomas arrives at Lower Tidmouth in time to show the Vicar's Sunday School to Percy. Near the end, Percy arrives at Elsbridge where Thomas cheers for him.
- Disneyfication: In the novel version of the story, Percy's train merely consisted of Annie and Clarabel, meaning that Percy's driver and fireman had to chop up some of Clarabel's floorboards to use as firewood for Percy's boiler. In this adaptation, a non-sentient brake van is added to the train, and Percy's driver and fireman are able to get floorboards from it.
- I Gave My Word: Percy was determined to get the children home in spite of the storm.
- Jerk with a Heart of Gold: Harold, who was rivalistic towards Percy in their previous encounter, sends supplies to help his train journey through the flood.
- Series Continuity Error: Due to being adapted later than "Percy Takes The Plunge" which refers to events from this story.
