When Kendra discovers that the key to a vault that holds one of the hidden artifacts is in the dragon sanctuary of Wyrmroost, the Knights of the Dawn prepare to enter the extremely dangerous sanctuary in order to get the key.

Seth attempts to halt a plague that is turning Fablehaven's beings of light into creatures of darkness, while his sister Kendra and the Knights of the Dawn attempt to retrieve an artifact before the Society of the Evening Star.

When the hunt for his lost friends leads Cole Randolph to the kingdom of Elloweer, he and new friends Mira, Twitch, and Jace team up with the resistance movement to search for Mira's sister, Honor, but enemies abound and Cole and Mira must use a new kind of magic to protect themselves.

After Jason succeeds in finding a way back to Lyrian, he's immediately in more danger than ever. Meanwhile, Rachel and the others have made their own progress--as well as discovered new enemies. As the group ultimately rejoins, they strive to convince their most needed ally to join the war and form a rebellion strong enough to triumph against the emperor.

Departing from the underwater dragon preserve of Crescent Lagoon to seek help from the Giant Queen, Kendra and Seth arrive at Titan Valley, where dragons are kept as slaves and made to fight in a gladiator-style arena.

As the evil Celebrant conquers more and more dragon sanctuaries, Kendra must raise an army of friends and allies on her own to fight him because her brother Seth and Bracken are missing.

When Kendra and Seth return to Fablehaven, they discover that Grandpa Sorenson has asked three specialists to protect the property from the Society of the Evening Star, a group determined to steal an artifact of great power from the preserve.