Thirteen-year-old Emma Murry has three goals for summer vacation: finish her art terms project, land an ollie, and help the environmental club save the monarchs.

But then her Instagram crush Jeb Scott and his celebrity dad Chester make a surprise visit to Black Mountain. At first, Emma is thrilled, then she overhears their plans to destroy the monarch butterfly garden to build a ski resort. She and her best friend Sophie add a new summer goal: STOP. THE. SCOTTS.

Ignoring Sophie's warnings, Emma makes friends with Jeb, convinced she can change his mind. So when Chester receives a mysterious death threat, Emma and Jeb team up to find the culprit. Emma slowly realizes people are not what they seem as she attempts to untangle friendships, organize a protest, and uncover the supernatural secrets hiding on the mountain.

She must go through her own metamorphosis by overcoming her fears and facing what she dreads. If she fails, she could jeopardize everything-butterflies, friendships, and her family.