Heroes of Olympus The House of Hades #4

Lost in the depth of the Underworld, Percy and Annabeth’s lives rest in the hands of their 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 ever again. 
But between them and the doors lies a vicious army hell-bent on destroying Camp Half-Blood…and the 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… Wwell, it’s only the whole world at stake.