Lost in the depths of the Underworld, Percy and Annabeth's lives rest in the hands of their friends and fellow demigods - Jason, Piper, Leo, Hazel and Frank.

Their five friends must reach the Doors of Death - gateway to the Underworld - if they ever want to see Percy and Annabeth again. But between them and the doors lies a vicious army hellbent on destroying Camp Half-Blood... and the whole world with it.

If the demigods can fight their way through- and Percy and Annabeth can survive hell itself - they might just have a chance.

If they don't... Well, it's only the whole world at stake.