The magical preserve Fablehaven provides refuge to numerous mystical species: centaurs, trolls, satyrs, ogres, fairies, minotaurs, brownies, imps, nymphs, and many others. But some beings are too large and powerful to be confined to regular enchanted refuges. These mightiest of creatures dwell inside the dragon sanctuaries.

At the end of the school year, Kendra and her brother, Seth, find themselves racing back to Fablehaven, a refuge for mythical and magical creatures where their grandfather is caretaker. The Society of the Evening Star, an ancient organization determined to infiltrate the preserve and steal a hidden artifact of great power, is storming the gates.

"Very strange things are afoot at Fablehaven. Someone or something has released a plague that transforms beings of light into creatures of darkness. Seth discovers the problem early, but as the infectious disease spreads, it becomes clear that the preserve cannot hold out for long. In dire need of help, the Sorensons question where to turn. The Sphinx has always given sound advice, but is he a traitor? Inside the Quiet Box, Vanessa might have information...

Whisked through a portal to The Outskirts, an in-between world, sixth-grader Cole must rescue his friends and find his way back home--before his existence is forgotten.