I can see the appeal here even with the familiar set up. Our protagonist is trying to prove her worth to those around her. Add in a strained relationship with her brother, a long missing person, and small town secrets and there's plenty there to support a plot. The actual writing is a bit stiff and unnatural but a I can see where a young reader might enjoy it.

Finley Walsh wants desperately to be an adventurer; she and her best friend Sophie had a books with the 100 top female adventures, and spent a lot of time thinking about places they go travel. Lately, though, Sophie doesn't want to think about adventuring as much. When Finley's mother has to go away for work, she contacts her cousin Jeff to watch Finley and her older brother Oliver and younger brother Quinn. Even though they haven't been in contact for a while, cousin Jeff is glad to help out, since the children's father has moved away and isn't very helpful. Arriving at Stone Creek, Finley is excited that there local mystery; after finding a treasure as a child, Meggie Riley disappeared one night. There are lots of theories, and the town's economy is heavily bound to the tourists who come and want to find out more. Finley sees this as an opportunity to finally have a REAL adventure, and thinks that this will entice Sophie to be friends again, and also encourage her mother to rely on her as much as she relies on Oliver. Jeff is busy running a diner, so the children are able to spend a lot of time roaming around town, interviewing locals and also scouring the woods for twenty year old clues. They run into Jason, the son of Meggie's former boyfriend, and Oliver becomes very fond of him. Finley does manage to find some clues that no one else has unearthed, but these start to get her into trouble. When she starts to get mysterious phone calls and feels like she is being watched and stalked, it seems like a bad idea to continue with her search, but she doesn't let anything stop her, not even a family connection to the disappearance. Will Finley be able to solve this cold case and finally consider herself a "real" adventurer?
Strengths: A lot of my students ask for "true crime" stories because they listen to podcasts about things like the disappearance of Meggie Riley, so I can see this being a topic that they might pick up. There's the underlying friend drama with Sophie (even though we don't see her) as well as Finley's anxiety and her uneasy relationship with her mother that motivates a lot of her actions. The children are given a lot of freedome to roam about, and they have Jeff's little dog Malt to go along with them. The details about Meggie's fate get a bit gruesome, and there's some real danger and intrigue, which my students will enjoy. Oliver's crush on Jason is reciprocated, so there's a bit of light romance as well.
Weaknesses:Finley makes a lot of really poor choices, some of which endanger herself and others. I was deeply uncomfortable with the way the town exploited the Riley family's misery. Granted, they were the ones behind the yearly "festival", but Finley asking questions and spying on their house seemed intrusive. The cover is also a bit too cartoony for as dark as this got.
What I really think: Readers who liked this author's Pepper's Rules for Sleuthing will want to pick up this new mystery especially since it takes a dark turn. I'm debating, since Finley's behavior made me really uncomfortable. She spies not only on the Riley's, but goes through Jeff's possessions without permission, even though she just met him and he's doing her mother an enormous favor.