Percy and his friends have ten days to return Zeus's stolen property and bring peace to Mount Olympus.

Life in Sunrise Valley is tranquil, but beyond its borders lies certain death. A dangerous black fog looms outside the village, but its inhabitants are kept safe by an ingenious machine known as the dam. Pig's father built the dam and taught him how to maintain it. And then this brilliant inventor did the unthinkable: he walked into the fog and was never seen again. Now Pig is the dam keeper. Except for his best friend, Fox, and the town bully, Hippo,...

"Sunrise Valley is without a dam keeper, and time is running out. In less than twenty-four hours, the poisonous tidal wave of black fog will descend on Pig's home. While Fox, Hippo, and Van hurry east to warn the townspeople, Pig ventures on his own path. Pig is following a trail of clues that are inexplicably linked to his father, and now that trail is leading upward. What he finds on a floating island above the clouds will shake him to his core,...