In the sixth book of the Magykal series, Alther Mella has been Banished, a Darke Domaine engulfs the Castle, and a Darke dragon is on the loose. Septimus Heap must use all of his skills to save the Castle and the Wizard Tower from destruction: He must enter the Darke. But he cannot do this alone. With the help of Jenna, Alther Mella, Marcellus Pye, and Septimus's estranged brother, Simon Heap, Septimus and Marcia Overstrand battle the spreading Darkenesse. Will Septimus succeed in protecting his Magykal world?