Once, Imani swore to protect her home from the monsters roaming the desert. But now an even worse enemy threatens the Sahir, and as the Harrowlanders march south with their stolen magic, it is only a matter of time before the invasion begins. The only chance for survival is a dangerous alliance with Qayn, a djinni king. If Imani journeys with him on a quest beyond the sands to restore his lost powers, he will summon a supernatural army to save her people. Meanwhile, her rival, Taha, has been captured and is on a dangerous mission of his own. One wrong move could cost them their lives - and everyone they love. But they may find that there is more than meets the eye crossing the Serpent Sea - and betrayal cuts deeper than any dagger.