When Jack and Annie travel back to the Kansas prairie in search of "something to learn," they gain an understanding of how hard life was for pioneers and they experience the terror of a tornado.

Years ago, Kahlen was rescued from drowning by the Ocean. To repay her debt, she has served as a Siren ever since, using her voice to lure countless strangers to their deaths. Though a single word from Kahlen can kill, she can't resist spending her days on land, watching ordinary people and longing for the day when she will be able to speak and laugh and live freely among them again. Kahlen is resigned to finishing her sentence in solitude... until...

When Camp Half-Blood, the only safe haven for demigods, comes close to being overrun by mythological monsters, Percy must find his best friend Grover, who is prisoner on an island in the Bermuda Triangle, and then set out to save the Camp.