After receiving a frightened message from her brother, Cara and her two best friends sneak out to his camp for genius children. There they discover more secrets about Cara's missing mother and the magical environmental war that is brewing. While there is danger and magic, the real appeal is Cara's realistic voice as she fights to protect her loved ones.

The seemingly three-tiered conflict that emerged in Fires Beneath the Sea (2011) coalesces into a single war in this earnest but somewhat haphazard middle volume. Cara and her brothers (though not their oblivious dad) know their mom's involved in a confrontation that connects murderous mythical creatures with global warming. Cara leaves Cape Cod for a Boston swim meet, but a frightened text from Jax (a classic genius-younger-brother archetype--think Charles Wallace from A Wrinkle in Time) says he's endangered at his Cambridge genius-kid camp. She sneaks off to fetch him, and a man with flames inside his mouth accosts her on the subway. He's a Burner, an elemental who belongs to the army of the Cold. The Cold steals people's consciousnesses (including Jax's) and uses their bodies as "hollows" to serve his Carbon War, which is acidifying oceans and extinguishing species. On the good side are mindtalking/mindreading teachers, Cara's mother (a shapeshifter) and animals both modern and ancient. Relevance to real-world burning of coal and other fossil fuels is vast. However, characters' naiveté and ill-fitting metaphysics (for example, a book that can take Cara anywhere she asks) replace the luminous prose and luscious, cohesive mysteries of the earlier book. Textual insistence on (Arthur C.) Clarke's Law--that magic and technology are indistinguishable--jams the nightmare-image Burners and other fantasy elements into the category of "tech." Nicely serious eco-fantasy; may volume three have more cohesive internal logic. (Fantasy. 9-13)