"Percy Jackson is about to be kicked out of boarding school...again. And that's the least of his troubles. Lately, mythological monsters and the gods of Mount Olympus seem to be walking straight out of the pages of Percy's Greek mythology textbook 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." -- from front jacket flap.

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.

Most people get presents on their sixteenth birthday. I get a prophecy that could save or destroy the world. It happens when you're the son of Poseidon, God of the Sea. According to an ancient prophecy, I turn sixteen and the fate of the entire world is on me. But no pressure. Now Kronos, Lord of the Titans, is beginning his attack on New York City. And the dreaded monster Typhon is also heading our way. So it's me and forty of my demi-god friends...

In his continuing quest to earn college recommendation letters from the gods, Percy has to pet sit the goddess Hecate's polecat and giant mastiff during Halloween week.