When Tessa, a single foster mom, is charged with the care of Astrid, an abandoned teen witch, the world as she knew it disappears. Discovering secrets about her lost foster child Theo, Tessa follows Astrid and a fabulous witch named Cece to a magical house. There, she joins the ranks of Magix, including a burly siren, a snake-charming ogress, a morbid little vampire, a pair of wild werewolf toddlers, and a coven of ice fairies, all of whom are in hiding from a murderous organization hell-bent on destroying the magical and non-magical worlds alike.

Interwoven with Tessa's journey is the story of three friends: Val, Tish, and Gunner. Letters between the three outline their work to prevent a looming climate crisis at all costs. As their story collides with Tessa's, it becomes clear that Tessa, Astrid, Cece, and even sweet Theo are mixed up in something far more sinister than they realized. Tessa must set aside her disbelief, fear, grief, self-doubt, and even her growing infatuation with Cece to join Astrid on a journey to find her family, finding her own family and the truth of herself along the way.