Every world knows the laws of balance. Push and pull. Ebb and flow. Rise and Fall. But the balance of Aos has begun to change… The Fall pulls down ships and their crews faster than they can be recovered, Dominique's brother among them. The Rise pushes a wall of water slowly but surely towards the prosperous city of Rihurr, and Theobald is the only one who notices. The oceans are unpredictable and perilous, forcing pirates onto land and driving Luke far from home. And in the middle of it all, the Daughters of the Moons look for answers, sweeping Ana up in their wake. For better or worse, their destinies align. The fate of Aos hangs on a knife edge, and they are all that stands between it and disaster. They must travel further than they've ever ventured before to answer one question: In a world of balance and song, what — or who — is tipping the scales?