War comes to Elmhurst. After facing charges of treason and the threat of hanging, Taryn is gravely injured, and the biomatons narrowly escape with their lives. With the biomaton rebellion officially declared, Elmhurst is preparing for war. Freshly awakened from a weeks-long coma, Taryn must battle not only the outside forces that want to subdue her, but her own internal strife as she realizes the full cost of war. She's learning new things about her past, losing friends, and worst of all, she's afraid she might be losing herself. Yet more pressing conflicts vie for her attention. While she's trying to run a rebellion and get her strength back, Erikkson insists an important player is missing—his third and most volatile construction: a clockwork assassin known as Petrichor, freshly returned after years in the United States. Taryn not only has to grapple with her own role and tenuous humanity in this war; she'll also have to face a new threat from inside her own army. Is freedom finally within reach, or will the biomatons find themselves in chains once again? Petrichor is the heart-pounding conclusion to the Children of Erikkson trilogy.