Off the Rails, retitled Gordon Takes a Dip in American releases, is the twenty-fourth (twenty-fifth in original broadcast order) episode of the first series. It is based on the story of the same name from the Railway Series book Gordon the Big Engine.
One morning, Gordon is resting his eyes at the station while noting to himself that being an important engine can sometimes be very tiring. Henry suddenly pulls up and rudely wakes Gordon. Gordon is very cross, believing that an engine who has never had an accident should be respected. Percy arrives next and asks if jammed whistles and burst safety valves count as accidents. Gordon denies it, saying that those sorts of malfunctions could happen to any engine, not like Henry who came off the rails.
It is Henry's day to take the Express. As he prepares to leave, Gordon reminds him not to come off the rails, much to his annoyance. When Henry leaves, Gordon tries to go back to sleep, but then his driver wakes him telling him that they have been asked to pull a special goods train. Gordon scoffs at the idea of having to take trucks, as he would rather take coaches.
Gordon's fire is unable to burn right away, so Edward comes to push him to the turntable to be turned around. Gordon complains the whole way and Edward rebukes him as they reach the turntable. By now, the movement has gotten Gordon's fire burning nicely and making steam. As the turntable turns, Gordon is so cross that he is willing to do anything that stops him from taking the special regardless of the consequences. When the table gets halfway round, he moves forward in an attempt to jam it. However Gordon is unable to stop and slides down some unused rails into a ditch, horrified, he shouts for someone to get him out but his crew sternly refuse and tell him that he is stuck.
In his office, the Fat Controller receives a phone call from Gordon's driver and is told all that has happened. Seeing Gordon derailed from his window, he orders to have Edward take the special train and leave Gordon where he is for now. Meanwhile; some little boys come by, see Gordon's predicament and start to tease him with a rhyme, leaving him humiliated.
Gordon stays in the ditch for hours and no rescue team comes until late at night. After extensive work preparing sleepers to keep him out of the mud, he is pulled out from the ditch by James and Henry.
Afterwards, a filthy and disgraced Gordon crawls back to the shed, much sadder and wiser for his experience.