When a struggling student teacher assigns a group project, seven-year-old Just Grace gets so involved in working with Grace W. and Grace F. that she fails to understand why she and her best friend, Mimi, are drifting apart.

Grace can do a lot of things ... but can she save the planet? Or at the very least, can she help her best friend Mimi get her favorite stuffed animal back? Lots of exciting things are happening to Grace and her friends. Most exciting of all, Mimi's older cousin Gwen is coming to stay with Mimi, and Miss Lois's class is going green! For their "green" project, Grace and Mimi aim to inspire their friends and classmates to conserve plastic bottles. But...

Eight-year-old Grace is excited to learn that her best friend, Mimi, is going to become an older sister, but when both try to be "mother's helpers" for a family renting a house on their street, little Lily likes Grace best, causing Mimi to doubt herself and Grace to form a plan to fix things.

Although disappointed at not being chosen to be the flower girl in her best adult friend's wedding, third-grader Grace plans a special surprise for the big day.