#7 The Mysterious Code by Kathryn Kenny, 1961.

The title is a little misleading because the code is really only a mystery for a small part of the book.

When the story begins, the existence of the Bob-Whites is threatened because there has been some vandalism at the school and there are fears of gang activity in the area. The school board is considering outlawing all clubs that are not directly supervised by the school and do not serve a specific purpose.

The Bob-Whites explain to their principal that they are a club that supports benevolent causes, but the principal says that they must demonstrate that they support something specific. Trixie suggests to the others that they raise money for UNICEF because it is a good cause and something that the school board would approve of. The Bob-Whites decide that they will hold an antique show to raise money, and they get people to donate items for them to exhibit and sell.  Honey’s mother says that they can have some things that were left in their attic by the former owner of the Manor House.

In the attic, Trixie finds a key with a tag on it. The tag is covered with a bunch of little stick figures, which turns out to be a form of code (one that fans of Sherlock Holmes would be likely to recognize). The key opens a box hidden in the attic, which contains a treasure that will raise a considerable sum of money for their cause. However, there is more mystery to come.

While Trixie and her little brother are on their way home from picking up an antique lap desk from a neighbor, they are attacked by three robbers, who steal the desk. A set of samurai swords is also stolen from the Bob-Whites, and someone attempts to burn their clubhouse. Can they find the criminals and recover the missing antiques, or will their antique show be ruined?