The gals all have some random friend named Elsa. Elsa works at Green Spring Pony Club, which Mrs. Rogers operates. I have no knowledge whatsoever about horseback riding, but I'll try and explain how it works. The clubs function like riding camps but select an elite team of kids to join a rally team at the end. That team competes against others for a prize. Mrs. Rogers established a scholarship program that lets kids who can't afford the camp come in and stay. She even provides them with horses and riding gear if they need it.
While riding with George and Elsa, Nancy's horse falls in a horse and nearly throws her. It becomes clear that someone deliberately dug the hole in the ground. Elsa then confesses that other things happened. Someone lost their gear, someone else had a minor accident, and a horse got spooked. Elsa volunteers to talk to Mrs. Rogers on Nancy's behalf and gets her and George jobs working for the club. They just lost a counselor and some campers because of all the strange stuff. Elsa even gets Bess an internship with some random equestrian newsletter that lets her cover riding fashions.
The first potential suspect is Clare, but only because they hear her threatening this kid Rafael and making fun of him for being poor. She actually tells him that he can't beat her and get a spot on the team because he doesn't have gear or a horse like she does. Mrs. Rogers warns her that if she isn't nice to the other kids, she might lose her spot in the club and never make the team.
Strange stuff happens right away. Someone writes a threatening note on Nancy's car, and she thinks it was Clare because the girl was supposedly in town and visiting with her brother at the time while they had an eye on everyone else. Someone spills oil all over the pool, and a girl almost breaks her arm when she slips on it. Rafael also finds that someone destroyed his saddle. Mrs. Roberts offers to replace it for free and sends Nancy and Elsa into town.
They get to meet Charlotte, the woman who owns the town's only equestrian store. She seems really nice and friendly but isn't a fan of Josh Bryant. He owns a pony club that is close to theirs but separated by a patch of woods. Charlotte offers to help Bess with a story on the latest fashions and kind of teases her about crushing on James, one of the counselors at the club. I only bring this up because it matters later.
Someone also called in a complaint that the horse barn wasn't up to local fire codes, which makes it a little strange when a fire breaks out. They save all the horses, but the fire department does tell them that the barn was totally up to code before. Nancy then finds a pen engraved with the initials JB on the side. Mrs. Rogers agrees to let them talk with Josh Bryant and even gives them directions on how to get to his house through the woods.
They follow the path but take a wrong turn and wind up trying to cross a raging river. If it were anyone else but Nancy, the person would die, but it's Nancy so she survives. They find a camper at the club who tells them all about how it sucks so much. Bryant doesn't help them or give them the advice that they need, he makes them spend all their time taking care of his horses, and he leaves them alone a lot.
The girls head inside and snoop around, but when Bryant comes home, Nancy hides in a dumbwaiter. He naturally finds her and accuses her of trying to set him up or of accusing him of something. Bryant tosses both her and George out of his house and tells them to never come back. He also makes it clear that he thinks he has the much better club.
Mrs. Rogers then gives Nancy permission to snoop around the club. That's when she finds a bottle of olive oil in Clare's dresser. Clare claims that she drinks a small amount every day to make her skin and hair look better, throws a massive fit, and demands they let her go. Since it's fast approaching the big competition of the summer, they let her go.
Whoever keeps doing all this crap continues at the competition. The person replaces markers on a path to make the Green Spring club go in the wrong direction and then hides some of their clothing. Nancy spots Charlotte in the crowd and sees her giving money to James. When she tries to ask her a question, Charlotte books it.
After a chase that lasts for way too long, Nancy finally catches her and gets the truth out of her. Charlotte's mom started the equestrian store and had a ton of money. She was also the best friend of Mrs. Rogers and thought her scholarship was just amazing. When she dies, she left half her fortune to the club. Her will stipulated that if the club ever closed, the money would go to Charlotte for her to open her own club and that if her club failed, she would get the balance.
Charlotte figured she could get the club to shut down, open her own shitty club, and get all the money when her club quickly closed. James's brother was at the other club, and James offered to help her because it would make his brother look better or something. Nancy tells the cops what happened and then Mrs. Rogers. They're all on hand to see her club win the big competition.
*Nancy laughs at George for saying she'd love to join the club because it's only open for 14 to 17 year old kids. Yes Nancy, because there's such a huge age different between a 17 year old and and 18 year old.
*Multiple people point out that there isn't any real difference in the clothing that riders wear during competition, so it doesn't make sense that the newsletter Bess works for has an entire column about fashion.
*Bryant is the owner of a pony club, but when his own club doesn't qualify for the competition, they agree to let him be one of the judges, despite the fact that he tells multiple people how much he hates Rogers and her group. How is that fair?
*The end reveal in this one was super disappointing. Charlotte is seriously only in that scene at her shop, and James is only in one other scene, though Bess does talk about him a little.