Stranded deep beneath the Sealed Archive, Allen faces down the "angel" possessing his student Stella. Physically and magically exhausted, the young tutor’s chances seem slim without help. Unfortunately, rescue won’t be forthcoming—his friends on the surface have their own crisis to solve. A rampaging Great Tree threatens to engulf the royal capital in deadly foliage, and the kingdom’s armies rally to the city’s defense. The dukes have sworn to avert disaster at any cost—including Stella’s life.
To save their tutor and their friend, Allen’s remaining students must brave an ancient and secret route beneath the palace and uncover the secrets of a princess erased from history—and they have competition. Church agents race to claim the angel for their own sinister ends, and one wears a familiar face. Can Allen bring himself to face an old friend from beyond the grave?