Capture the Flag by Kate Messner
The flag in this story is the one Betsy Ross made during the Revolutionary War which happened even before I was born. Anna, Jose, and Henry don’t know each other at the beginning of the story. They are in seventh grade and too young to leave home alone and too old for a babysitter so they have to go to the fancy party at the Smithsonian Museum. It’s at that party where the flag is stolen. And it will be the three of them who expose the real criminals. They also learn about the Jaguar society.