"The Greek and Roman demigods must simultaneously prevent the earth mother, Gaea, from waking and stop war from breaking out at Camp Half-Blood"-- Provided by publisher.

At the conclusion of The Mark of Athena, Annabeth and Percy tumble into a pit leading stragith to the Underworld. The other five demigods have to put aside their grief and follow Percy's instructions to find the mortal side of the Door of Death. If they can fight their way through the Gaea's forces, and Percy and Annabeth can survive the House of Hades, then the Seven will be able to seal the Doors from both sides and prevent the giants from raising...

Uniting with Jason, Piper, and Leo after their dangerous quest, Percy, Hazel, and Frank wonder who will be chosen to fulfill the Prophecy of Seven, completing their group's number, and sail with them to an ancient land to find the mysterious Doors of Death.

"When mysterious incidents start wreaking havoc throughout Camp Jupiter, suspicion falls on the Fourth Cohort's newest probatio. But is she really to blame? Find out the truth by delving into the pages of her personal journal."--