On Lucy's first day of second grade, she's excited to meet her new teacher, Miss Flippo, and find out everything's she's going to learn about this year in school. And when Miss Flippo tells the class that they're going to have their very own science lab, complete with lab coats and goggles, Lucy can't wait to start exploring.

But one thing is troubling her. The tree that sat outside her first-grade classroom all year is gone. Where are the squirrels going to live?

Inspired by her classroom lab, Lucy starts her own research mission to find out what happened to the tree, and then to lobby for the school to plant a new one. With the help of her cousin, Cora, and their new classmates, Lucy discovers that science is everywhere you look, and a lab can be anywhere you look.