How does Percy get the tree pearls?

In the "Percy Jackson" series, particularly in "The Sea of Monsters," Percy retrieves the tree pearls from the goddess Circe. After a series of challenges, he is guided by the prophecy and the advice of his friends. The pearls are enchanted items that help demigods escape from danger, and Percy uses them to free himself and his companions from the clutches of the Cyclops, Polyphemus.