Horrible things are happening in Fever Swamp, and everyone thinks Grady's new dog is responsible, but Grady knows his dog is a regular old dog that doesn't change into a terrifying creature when the moon is full. Or does he?
The long-awaited prophecy surrounding Percy Jackson's sixteenth birthday unfolds as he leads an army of young demigods to stop Kronos in his advance on New York City, while the Olympians struggle to contain the rampaging monster, Typhon.