Mary Anne has been feeling lonely with Mallory and Dawn, who are still absent from the club & Logan is too busy with volleyball to spend time with her. When Mrs. Kishi asks the BSC for volunteers to help with the Readathon that the library children’s room is sponsoring, Mary Anne accepts because she loves reading and is really looking forward to helping other kids love it too.
The first day goes off well, but on the second day, there are a bunch of people outside of the library protesting books they want banned. Mary Anne wants to stop and talk to them to figure out why they’re protesting, but doesn’t want to be late for while. While helping Charlotte Johanssen and Rosie Wilder pick out some books, the fire alarm goes off after someone sets a fire in the sink of one of the bathroom. A week later, another fire is set in a garbage can outside of the back door, but it’s more serious than the first fire because lighter fluid was used to set it off.
As the BSC investigates the case, Claudia learns that the land that the library sits on used to belong to a family that ran into some financial trouble; they sold the land to the town with the condition that a library be built on it and if the library was destroyed or torn down, the land would be returned back to the original owners. The family’s name is Ellway, which is the name of the new assistant children’s librarian, who isn’t quite pleasant, so the girls suspect that she might be responsible for the fires.
When Mary Anne helps Nicky Pike find some books and look over his selections, Nicky knocks his jacket over and a box of matches falls out of it. Nicky insists that the matches don’t belong to him and doesn’t know how they got there. Mary Anne believes him especially when another fire is set in a trash can outside another door to the children’s room & another book was used. Mary Anne realizes that each and every book that was used to start the fires is on the list of books that the protestors are trying to get banned.
Mary Anne and Kristy decide to interview one of the book banners, pretending they are from the SMS newspaper. Kristy asks one of them, a woman named Bertha Dow if she had ever burned books before. Ms. Dow admits that she has, but the publicity was so bad, she figured that it wasn’t the best way to get her message out there. Mary Anne isn’t sure anymore that the book burners are responsible, but she finds another clue: each book (in addition to one that the protesters want to be banned) is also on the 5th grade reading list for the Readathon.
The girls figure out that there is only one location left for the person responsible for the fires to burn a book and that is a trash can near the reference area where there is a biography about Abraham Lincoln on the list which is shelved nearby. The girls decide to stake out the area the next time they’re at the library. They discover Sean Addison is responsible for the fires because his parents are forcing him to be in the Readathon when he doesn’t want to and he doesn’t like how his parents push him and his sister, Corrie into various activities. In the end, the Addison family ends up in counseling and when the prizes for the most books read in each grade are announced: Mathew Arnold, Sarah Hill, Marilyn Arnold, and Nicky Pike all win in their grades.
The Stoneybrook Library children's room is holding a Readathon to raise money for new books. And Mary Anne, who loves to read, is helping out by finding good books for the kids to read.
But things and the library get really scary when small fires break out. The police know the fires have been set. But by whom? And why would someone want to burn down Stoneybrook's library — especially when there are tons of kids around for the Readathon?
This is one serious mystery that Mary Anne's not going to let go unsolved!