First off, a quick Context Lesson: This priory school is basically a fancy boarding school for boys. This school, and others like it, functioned as prep schools for boys heading off to college someday. By the 1890s, England did have mandatory public schools, so poor kids got at least some education. Richer kids went to fancy prep schools, though, and were pretty much the only ones attending college. Also, girls got basic education in this era, but higher learning institutions often didn't allow women to attend. It was very rare and very difficult for a woman to get a college education. There weren't really any "priory school" equivalents for women in this period. If you're interested in learning more about schools and education in Victorian England, go here.
On with the story.
A guy with the best name ever, Dr. Thorneycroft Huxtable, barges into Baker Street and promptly passes out, causing a small earthquake since he's a big guy.
Dr. Huxtable comes around and apologizes for his overly dramatic entrance.
Holmes says no problem since he is melodramatic himself and can't really pass judgment.
They get Dr. Huxtable some milk and cookies to help revive him. No, really.
This is already the best story ever.
So after having a snack, Huxtable explains what the problem is. He's the head of a fancy-pants prep school. One of his students, the son of the super wealthy and important Duke of Holdernesse, is missing.
The Duke has tried to keep everything out the papers to avoid a scandal, but Huxtable decided to call in Sherlock Holmes to help.
We get some background on the Duke now. The Duke's marriage hasn't been happy and he and his wife are separated. She now lives in France and the Duke sent his ten-year-old son off to the Priory school in the hopes of getting his mind off his mom.
Historical Context Lesson! While you may think there are shades of Kramer vs. Kramer here (where the mom says "see ya" and runs off, leaving the kid with his dad) that probably isn't the case here. In this era, children automatically "belonged" to their father. So anytime there was a divorce (very hard to get) or a separation (easier to manage for the wealthy) the dad had automatic custody rights to any children. The dad would have to agree to let the kids stay or go with the mom. In this case, the Duchess apparently decided not to fight the issue and let her son stay with his father, perhaps so that he could attend school in England. We never really find out exactly what went down there. If you want to learn more about marriage in the Victorian era, check out our theme section on "Marriage."
Back to the mystery. The boy, Lord Saltire, disappeared a few days ago. The school's German teacher, Professor Heidegger disappeared as well and the professor's bike is missing.
There's no trace of either of them and Huxtable is very worried.
Holmes agrees to take on the case and grills Huxtable about some details.
We learn that the Duke's secretary James Wilder is the one who filled Huxtable in on the Duke's marriage. Lord Saltire sided with his mom.
We also learn that Lord Saltire got a letter from his father the day he disappeared.
Later Holmes and Watson arrive at the Duke's house to question him.
The Duke is not happy to have a PI on the case. But since Holmes is already there, he tells him he can work the case.
The Duke has no helpful information, so Holmes and Watson leave to investigate the school and the nearby roads.
The next day Holmes gets back on the trail and he and Watson start tracking bicycle tracks. They find evidence of two different tire tracks. This is just like CSI.
After a lengthy search they find Heidegger's body.
Holmes determines that Heidegger must have seen Lord Saltire being kidnapped and chased after him on his bike.
Whoever kidnapped Lord Saltire killed Heidegger and left his body.
The dynamic duo then follow the other set of tracks to an inn called the Fighting Cock, and it seems pretty crummy.
Holmes and Watson question a mean old guy named Reuben Hayes, the owner of the inn.
Holmes lies and tells Hayes that they have traced Lord Saltire to Liverpool.
Hayes slips that he has it in for the Duke because the Duke fired him once upon a time.
Holmes and Watson leave him and poke around some more in his barn. Holmes observes his horses.
Hayes comes back and yells at them for spying, so and Holmes and Watson hightail it out of there.
After leaving they see James Wilder frantically riding his bike to the inn.
Watson and Holmes sneak back to the inn to spy some more. Hayes and Wilder are talking together.
The next day Holmes and Watson go back to confront the Duke. Holmes has solved the case.
Before he does his tell-all spiel he makes sure that he'll be getting the Duke's reward money for the case. Watson notes that this is unusual for Holmes, who normally doesn't care much about money.
They confront the Duke and Holmes accuses Hayes and Wilder of kidnapping the Duke's son. He also says that the Duke knew all about it.
The Duke admits everything and then proceeds to shock Holmes with his confession.
Turns out, James Wilder is the Duke's illegitimate son.
James was jealous of his younger brother and was angry that he wasn't the Duke's heir. But, legally, the Duke can't leave his estate to an illegitimate child.
James lied to his younger brother and told him that his mom was back in England and wanted to see him.
So he lured Lord Saltire, whose first name is Arthur, from the school. Arthur met with Reuben Hayes, who had a horse for him to ride.
But Heidegger chased them and Hayes killed him.
Hayes dropped Arthur off at the inn and left him under the care of Mrs. Hayes.
After James found out about Heidegger's death he confessed all to the Duke.
The Duke agreed to keep James's secret for three days so that Hayes could escape.
He went to check on his kid, who was traumatized, and then left him at the inn. Worst dad ever.
At least, Holmes seems to think so, and he tells the Duke off.
We also learn that James helped to break up the Duke's marriage to Arthur's mom.
Holmes reveals that Hayes has already been arrested, and that he won't reveal James's part in all this as long as the Duke throws James out. And he throws him way out too: he's shipping him off to Australia.
The Duke agrees to all this and says that he's contacted Arthur's mom and hopes to fix his marriage.
Holmes then collects his reward money. Watson implies that Holmes did this as a dig to the Duke for being such an awful father.