In this high-octane conclusion to the Unseelie duology, which Andrew Joseph White calls "a portal to a world of glimmering fae and blistering magic," two sisters discover that the things that make them different can lend them more power than they ever imagined. Isolde Graygrove has always put her changeling twin sister first. But ever since Seelie returned from the faerie realms with a newfound confidence in her magic and secrets she's keeping even from her twin, Isolde can't help but wonder: who is she, if not her sister's protector? Seelie knows there are some problems even magic can't solve. Like the distance between her and Isolde, the terror of her growing and unfamiliar emotions for Raze, or the fact that the world's last firedrake has imprinted on her like a baby duckling. Still, she can't help but try. When Seelie accidentally splinters the three realms, tangling the human and faerie worlds together into something new, the vicious faerie Gossamer is determined to take full advantage of the chaos unleashed. Seelie and Isolde will need to spill their secrets, decide who they can trust, and navigate the sinister glamour of the faerie courts to save humankind and fae alike.