For this volume, Awdry had to write in Scots slang for a lot of the dialogue used by newcomers Donald and Douglas.  This book is the first indication we get of not all being well for steam on the Mainland, hence the fact Douglas has escaped with his twin's help for want of a future, and leaving the Fat Controller with the dilemma of what engine to keep, and which one to send back home again!

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‘Hullo, Twins!’
The Fat Controller’s Railway is becoming increasingly busy. No sooner has one train arrived, than it leaves as another. Everyone is feeling overworked, and the engines are grumbling about the constant Goods Work. So the Fat Controller promises that a Goods Engine from Scotland will arrive to help.

But the next day, the Fat Controller is given an unexpected surprise—it appeared that two engines had come instead of one. The Railway Director tries to work out which of them was Engine “57646”. But neither would tell who was who—they called themselves Donald and Douglas, after they had lost their names and numbers on the way. Determined to find out who is the malingerer, he orders the Inspector to send them to work.

 

The Missing Coach
The twins are both given numbers—Donald 9 and Douglas 10. When the painters leave, Douglas mentioned to his twin that, although they painted numbers on their tenders, they hadn’t put names on them!

Just then, the Inspector arrives, and says that Duck will show they around the Yard. The twins get on well with Duck, and even put Gordon and Henry in their place!

One of the carriages on Gordon’s Express is a Special Coach, full of people from England, Wales and Scotland, who want to travel on Thomas’ Branch Line. Every evening, engines have to remember to shunt the Special Coach to the bay Platform for Thomas to collect shortly, after the other coaches are taken away empty. One evening, Douglas offers to take away Gordon’s coaches in place for Duck. But he worries so much about being sent back to Scotland, that he forgets about Thomas’ Special Coach, which he shunts with the others into the carriage siding…

Soon, Thomas and passengers are complaining about the mix up, and Douglas is horrified at being caught out. But his driver has an idea—the engines swapped tenders, so as Donald, disguised as Douglas, leaves with a goods train, Douglas pretends to be Donald and no nothing about what has happened. After the Fat Controller has calmed down the passengers, he suddenly turns to Douglas, demanding why he is veiled with Donald’s tender…!

Break Van
After the coach incident, the Fat Controller is keeping an eye on both engines, seeing which of them shall stay. But Donald and Douglas are upset at this, so decide to work as good as each other—that way they’ll both have to be kept!

Unfortunately, a Spiteful Brakevan in the Yard takes an instant disliking for Douglas, and causes him endless problems, until Donald gives it a good bump and threat—the van’s behaviour soon improves. But then Donald has an accident when he crashes into a signal box, resulting in more problems for the Fat Controller, who was planning to send Douglas back and keep him! So, with Donald having his tender mended, James is enrolled with the goods work, which he grumbles about.

The Spiteful Brakevan, who is on James’ morning train, causes bother for the red engine, by telling the trucks to hold back. Douglas is at Edward’s Station as Poor James struggles wearily in, where he asks for help up the hill. Douglas is more than willing to do so, and the two engines force the trucks up the hill. Unfortunately, Douglas pushes a little too hard, resulting in crushing the Brakevan to smithereens!

The Fat Controller is more displeased with Douglas as he was with Donald, but Edward mentions of how hard working Douglas sounded from his yard, leaving the Fat Controller in an awful decision…should he keep Donald or Douglas?

The Deputation

Heavy snow has come to Sodor, blocking the lines with deep drifts. Donald and Douglas, however, prove that they’re more capable in snow as other engines are. Coupled back to back, with a van between them, and snowploughs on fronts, they patrol backwards and forwards clearing the lines best as they can, which they do very well in—the engines are pleased, especially Henry, whom they rescued when he got himself stuck!

But all is not well. The Twins gloomily tell the others that the Fat Controller might send both them away. Gordon, James and Henry protest at this and agree that something must be done for Donald and Douglas. When Percy asks Edward, he suggests in having a Deputation—in which engines tell the Fat Controller something is wrong and ask him to put it right.

So after Percy tells them about the “Depostation”, the others are very unsure. After a thought, Gordon announces that Percy shall be the “Disputation,” much to the little green engine’s shock.

When The Fat Controller comes back, Percy worryingly tells him about their “Desperation”, which makes up the Fat Controller’s mind for good. Next morning, he congratulates Donald and Douglas for their work in the snow, and offers them a new coat of paint, as well as having nameplates too. The Twins were surprised, until they realise that the Fat Controller has decided to keep them both. The rest of The Fat Controller’s Speech is drowned out as the Yard fills with delighted cheers and whistles!