When twelve-year old Jesse Hawthorn moves to a rural community with her emotionally distant father and bratty younger sister, she has a hard time trying to adjust in her new town. For starters, she is boyish looking and takes great pleasure in collecting crickets and other assorted insects. Jesse has also attracted the unwanted attention of Brenda Richards, a girl whose personal mission seems to be to complete Jesses misery by bullying and harassing her. To top it all off, she has just killed yet another one of her good friends; a woolly bear caterpillar that she had been keeping inside of a plastic bubble gum container in spite of the warnings from her science teacher, Mr. Jordan.

When Jesse reluctantly accepts an invitation to join the lunch table of her sympathetic neighbor Jacob and his two friends Howie and Lucille, she begins her transformative path of self-discovery. Along the way Jesse and Jacob take over an abandoned van, discover punk rock music, and the exhilaration of sneaking out at night. With the help of her teacher, Jesse finally learns the art of caring for and rearing a wooly bear caterpillar through all of the stages of its delicate development; from its larvae stage, through pupation until it is the night flying tiger moth it was destined to become. Through all of this, Jesse develops her own sense of bravery; one that will that guide her in a startling moment of standing up for herself against Brenda Richards and even allowing her to tolerate the blushing of a first romantic crush.