Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition (Initial Situation)
Two of a Kind
Tom and Edward are born. One is rich, and one is poor. The rich one is the Prince of Wales, and the poor one only dreams of one day even seeing a real-life prince. That's about all you need to know about these two kids.
Rising Action (Conflict, Complication)
Maybe That Wasn't Such a Good Idea
Tom and Edward meet, and coincidence of all coincidences, they look exactly alike. Since the grass is always greener on the other side, they agree to switch roles for just a little while. But unfortunately for the prince, things go way further than he expected. It's not so easy to convince everyone you're royalty when you look like a beggar and everyone wants to dump chores and abuse on you.
Climax (Crisis, Turning Point)
You've Got the Wrong King
King Henry VIII has died, and everything has been leading up to the coronation of the new king. Just when it seems that all is lost, and Tom will be forced to become King of England, Edward shows up. He convinces the court that he's the real king, and everything is gravy after that. This is both the tensest and the most awesome part of the whole book.
Falling Action
It's Time for Justice
Edward wraps up some of the story's loose ends. Miles gets his knighthood and his lady. Tom gets some special status—and freedom from his abusive father. All those silly archaic laws are abolished. Finally, stuff is starting to calm down in merry old England.
Conclusion
A Short Reign, But an Awesome One
Edward only reigns for a few years before he dies, but they are years marked by peace and justice. His memory lives on in the minds of English people.