As the Upperworld begins to fall apart, Onyx leaves his post as a guide and joins Luna on Earth. She needs protection from a mysterious assassin bent on bringing her ultimate demise. Together, Onyx and Luna learn to navigate the human world while dodging the sinister stalker who is bent on tracking her every move.

Above them in the Upperworld that Onyx left behind, the Most High Being is rapidly dying - and nothing can save him. If his death goes unchecked, the entire Upperworld, and all of humanity, will be at risk of extinction. As a last-ditch effort, Jade and Evander begin to organize the Disturbers - Upperworld dwellers who have the same goal in mind: taking Zephyr down before they are all banished to the Underworld with him. Will they succeed, or be dragged down to their doom?