Lillian is actually the Heart of Earth, its source of magic, and the Guardians have to protect her. Cornelia attempts to gain her sister's trust. Matt, Mr. Huggles, and Napoleon become the Regents of Earth. Cornelia is forced to babysit her sister while her parents are out for the night.

Phobos returns to Meridian and begins conquering it with his new powers. While the Guardians are trying to stop him, Hay Lin has to complete an art project on Xanadu, her vision of paradise. Meanwhile, she has also lied to her parents that Yan Lin left for a vacation in China to see distant relatives.