Nico di Angelo suffers a stigma as the only living child of hades: leaving him feeling as though he doesn't belong. But there was a time when he belonged, when his sister Bianca was alive. He is aboard the Argo II as his thoughts are focused on his dead sister. She is gone and it is his fault for not protecting her. What Nico doesn't know is Bianca is there with him, telling him to be her brave little soldier.

When Nico lets out all of his feelings, he unintentionally reveals his secrets to the other demigods on the Argo II. His friends, wanting to protect him, vow to help him. But what happens when Nico's worst fears run wild? Will Percy be able to save his cousin? Will Nico face his fears, or let them consume him?