Mythological monsters and gods of Mount Olympus seem to be walking out of the pages of twelve-year-old Percy Jackson's textbooks and into his life. And worse, he's angered a few of them. Zeus's master lightning bolt has been stolen, and Percy is the prime suspect. Now, he and his friends have just ten days to find a return Zeus's stolen property and bringpeace to a warring Mount Olympus.

When the goddess Artemis disappears while hunting a rare, ancient monster, a group of her followers joins Percy and his friends in an attempt to find and rescue her before the winter solstice, when her influence is needed to sway the Olympian Council regarding the war with the Titans.

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.