Libro   segundo de la serie Los héroes del Olimpo
 Tres amigos. Una misión de locos. Y un enemigo con poderes   sobrehumanos.
 ¿A qué juegan los dioses del Olimpo? Gaia, la madre Tierra, está   despertando a un ejército de monstruos para acabar con la humanidad... y   ellos se entretienen mareando a los semidioses, los únicos que pueden   derrotar sus perversos planes. Ahora han mandado a Percy al campamento   Júpiter casi sin recuerdos y con la inquietante sensación de que él, el   griego, es el enemigo. Por suerte, contará con el apoyo de Hazel, una chica   nacida hace más de ochenta años, y de Frank, un muchacho torpe que todavía no   sabe muy bien cuáles son sus poderes (ni si los tiene). 
Juntos deberán emprender una peligrosa expedición para liberar a Tánatos,   el dios de la muerte, de las garras de un gigante... 
ENGLISH DESCRIPTION 
 Percy is   confused. When he awoke after his long sleep, he didn't know much more than   his name. His brain-fuzz is lingering, even after the wolf Lupa told him he   is a demigod and trained him to fight. Somehow Percy managed to make it to   the camp for half-bloods, despite the fact that he had to continually kill   monsters that, annoyingly, would not stay dead. But the camp doesn't ring any   bells with him.
 Hazel is supposed to be dead. When she lived before, she didn't do a very   good job of it. When the Voice took over her mother and commanded Hazel to   use her "gift" for an evil purpose, Hazel couldn't say no. Now,   because of her mistake, the future of the world is at risk. 
 Frank is a klutz. His grandmother claims he is descended from ancient   heroes, but he doesn't even know who his father is. He keeps hoping Apollo   will claim him, because the only thing he is good at is archery. His big and   bulky physique makes him feel like a clumsy ox, especially in front of Hazel,   his closest friend at camp. He trusts her completely-enough, even, to share   the secret he holds close to his heart. 
 Beginning at the "other" camp for half-bloods and extending as   far north as the land beyond the gods, this breathtaking second installment   in the Heroes of Olympus series introduces new demigods, revives fearsome   monsters, and features other remarkable creatures, all of whom are destined   to play a part in the most important quest of all: the Prophecy of Seven.