Originally intended to follow the adventures of the Main Line Engines, most of the action in this book appears to centre upon engines connected or on Edward's Branch Line - particularly the twins Bill and Ben.  Highly amusing, and with some of the best Edward related plots of all.

The Diseasel
Bill and Ben the tank engine twins have a shock  when they find their trucks have mysteriously disappeared from their sidings.  A patch of oil left behind indicates that a Diesel has taken them - which Bill and Ben believe is somehow connected with a poster in their shed about spread of infection.
The twins set off to retreive their trucks, sans names and numbers to fool the theiving Diseasel.  When they find him, he's reluctant to listen to them and refuses to give up the trucks - which means the twins get to put their own plan into action and make the Diesel quite giddy.  Edward soon arrives and informs them that this is a newcomer called Boco, who wouldn't understand about their arrangements, and orders the twins to fetch trucks for him to make up for the misunderstanding. 
 
Buzz Buzz
Boco arrives at the sheds at the big station, where he meets Duck, who he tells about the twins' mishaps. The two of them are soon chatting happily, and Duck agrees that they can be a bother - he even calls them "The Bees".
James arrives in time to hear the nickname, and takes it to mean that Duck has a phobia of bees, and tells him not to be so silly and boasts that he wouldn't have any trouble getting rid of bees.
But the following morning when James arrives to take the Express, a white wooden box is broken open when two porters try to avoid a collision with an old woman.  The box turns out to be a bee hive, and it's inhabitants soon run amok in the Big Station, eventually settling on James' boiler, and when one burns it's foot - it stings James on the nose, forcing him and his crew to leave the station in a frantic hurry without the coaches.  In the end, Boco has to take the train in his place, whilst James becomes a laughing stock in the shed at the end of the night!
 
Wrong Road
Gordon is left disgruntled by Boco's handling of the Express, and questions why a Branch Line Diesel should be allowed to run a Main Line train, and remains indignant on the subject of Branch Lines.
The following evening, he and Edward are due to take two fast trains from the Big Station - but Gordon is sent off accidentally by a woman in floppy green hat - mistaking it for the Guard's green flag.  He has to be brought back before Edward can start, meaning he has to leave first instead.
However, the signalman at the junction doesn't receive word about the change, leaving Edward on the Main Line route and Gordon running onto the the Branch - where he's left for the rest of the night, and into the early morning when Bill and Ben find him asleep, and pretend they think he's a pile of scrap which they need to dispose of - much to Gordon's horror.  Luckily for him, Boco soon arrives to save the day, and Gordon to this day believes the Diesel to be his saviour!
 
Edward's Exploit

When some enthusiasts arrive on the railway, Edward is given the task of taking them to the China Clay Works on their last day, but encounters difficulties in starting, and on the way home, the stormy weather adds to the problems.
One of Edward's crank pins snap and damage his frame and splashers, leaving him and the passengers stuck on the Main Line.  The crew have to remove his side-rods, which makes starting again very difficult.  So in turn, they try something different - loosening the couplings between the coaches, so that Edward can pick his them up one by one.  This is exactly the help Edward needs, and eventually, gets the train moving and triumphantly brings it home to the Big Station, late but safe, and Edward is hailed a hero.