The series was based on The Railway Series, a series of books created by the Reverend W.V. Awdry. They deal with the adventures of a group of subanthropomorphised trains and road vehicles who live on the fictional Island of Sodor. The books were based on stories Awdry told to entertain his son Christopher during his recovery from the measles. Many of the stories are based on events from Awdry's personal experience.

Episodes in Season 3:
A Scarf for Percy
Percy's Promise
Time for Trouble
Gordon and the Famous Visitor
Donald's Duck
Thomas Gets Bumped
Thomas, Percy and the Dragon
Diesel Does it Again
Henry's Forest
The Trouble with Mud
No Joke for James
Thomas, Percy & The Post Train (Thomas, Percy & The Mail Train - US)
Trust Thomas
Mavis
Toby's Tightrope
Edward, Trevor and the Really Useful Party
Buzz Buzz (James Goes Buzz Buzz - US)
All at Sea
One Good Turn...
Tender Engines
Escape
Oliver Owns Up
Bulgy
Heroes
Percy, James and the Fruitful Day
Thomas & Percy's Christmas Adventure (Thomas & Percy's Mountain Adventure - US)