Faced with an impossible choice, Skylar and the other descendants embark on a deadly quest to the underworld to confront Hades, who has been plotting to kill them all. Â They discover the ancient gods are not dead, as once believed, but are instead held captive in a secret location. In order to save the world from destruction at the hands of Hephaestus, the descendants must rescue their ancestors, the gods of Olympus. Â Skylar learns more about her bloodline and her powers, but there is a heavy price to pay. The darkest forces known to man are about to return to reclaim their stolen kingdom.