User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-76.219.133.10-20130605154611

"If the hero is rescuing someone there will be a catch. For instance, in Greek mythology, Orpheus was told his love, Eurydice, would follow him out of Hades, provided he did not look back to check that she was there. He looked back right after he got out but before she did and lost her."

On the cover of House of Hades, Percy is looking back.

I'm going to cry.