The second book in the Adventures of the Elements series continues the five brothers and sisters adventures with the element guardians. The battle continues!Crossing the foreboding Valley of Forlorn Isotopes, Catherine and her brothers aid the element guardians in battling sinister isotopes in a life and death struggle to reach the Palace of Knowledge and the astonishing gifts it contains. Reaching and discovering the secrets of the palace and its inhabitants is only the beginning of the children's journey.For what is gained in the palace is all but lost in an unfortunate wrong turn into ancient Greece. Captured by thieves, separated, and sold as slaves, the siblings face the evils of humanity and the unforeseen perils of nature.