Thalia Grace, daughter of Zeus, has always fought for the gods and for what is good. But as the war between the Titans and the gods continues to escalate, she begins to doubt everything she has fought for. Losses and the coldness of the gods lead her to make a decision no one could have expected. When Thalia switches sides and joins the Titans, she becomes their most dangerous weapon. After all, she is about to turn sixteen - and according to the great prophecy, she will decide the fate of the world. On the side of the Titans, she faces her old friends as an opponent who knows the weaknesses of the heroes better than anyone else - a combination that makes her nearly unstoppable. Only Percy, her equal in power, might be able to stop her. But then, there's also the Ophiotaurus... Can anyone bring Thalia back - or will she be the one to seal the fate of the gods? A story about pain, power, and the question of what happens when belief breaks.