Annabeth Chase and Artemis, the goddess of the hunt, are kidnapped and Percy and his friends must find Artemis before the winter solstice. This is because at the winter solstice, her influence on the Olympian Council could change an important vote. The vote was on the war with the Titans. Thalia Grace, Zoë Nightshade, Bianca Di Angelo, and Grover go on this dangerous quest. They also are searching for a rare monster that Artemis was trying to hunt down when she went missing. This monster is so powerful that it can destroy Olympus. Percy is called by a hippocampus (which is a mythological sea-horse) to rescue a cow-like creature called the Ophiotaurus which lives in the sea. Percy names the Ophiotaurus "Bessie". He did not know that it is a male.