Percy the Post! is a magazine story.
Percy leaves the sheds with the expectation of pulling the mail train as usual. Then suddenly, Harold flies overhead carrying mail sacks in a net beneath him. He tells Percy that he's on post patrol so they don't need the little green engine anymore. Percy is not happy.
The next morning, Percy is delivering eggs to a supermarket, but wonders who is taking the mail. His driver tells him the post is going by air mail again. Percy is very upset; pulling the mail is his favourite job.
Later, a buckled rail forces Percy to use a bumpy old loopline. With so many eggs aboard, Percy can only go slowly. Then, Harold whirrs overhead with his net full of mail again. Sudenly, the cargo net breaks loose and falls. It plummets to the ground and the mail sacks burst open, sending letter flying everywhere. Harold hoveres lower and lower to land, but the wind from his blades blows the letter around like snowflakes. Percy pulls to a halt so that his crew can help Harold's pilot round up all the letters.
Soon, all of the letters have been collected. Percy worries that if he speeds along the bumpy old loopline, the eggs will be scrambled by the time they reach their destination. Harold has an idea and, carefully, the eggs are carried out of Percy's wagon and loaded into Harold. The helicopter's post is then put inside Percy's truck. Both Percy and Harold agree that mail going by rail and eggs going by air is the safest and quickest way for everything to arrive on time.