Diego is under the spell of the wizard Maldred who wants to control the Naga, an enormous dragon that lives deep within the Earth, and plans to use Diego to steal the two keys necessary for that purpose; the first key is guarded by Argent, the silver dragon, and Jean his dragon master, so Drake, Bo, Carlos, and their dragons travel to Gallia to try and stop the theft and break the spell on Diego.

Before she can start a new life in Virginia Beach, Carina Channing receives a mysterious key from her imprisoned father--a key her mobster uncle died trying to obtain. Following cryptic notes left by her father, Carina and her boyfriend Navy SEAL Jay Wellman go in search of the lock the key will open--but every step they take grows more perilous because there are others who will do anything to find the hidden location first.

Arthur's life is saved by a key shaped like the minute hand of a clock, but bizarre creatures from another realm are determined to take the key even if it means killing him.

The evil wizard Maldred has stolen the gold and silver keys which will allow him to release the Naga, the powerful earthquake dragon at the center of the earth--so Drake and several of the other Dragon Masters travel to the Naga's Temple in the Dragon Islands, to try and stop Maldred, and prevent him and the earthquake dragon from destroying the kingdom.

Neither Cleo nor Evan like the new school librarian, Ms. Crowley, but they are very curious about where she disappears to at the back of the library, so one day they follow her--and find a secret door, a magical library full of locked books, and a letter from the previous librarian telling them that she is trapped somewhere between the covers of one of the enchanted books, and they must travel through the stories in order to save her.

This time Cleo, Evan, and Ms. Crowley (who, it turns out, is the missing Ms. Hilliard's sister) find themselves in a confusing fantasy book, caught up in a war with wizards, elves, trolls, and the mighty Golden Dragon--and while they manage to find their missing librarian, their quest does not end there.

In their second trip through the enchanted library, the new key lands Cleo and Evan in the middle of a spy story, where their impossible mission is to stop a traitor who calls himself Viper--and they find themselves working with the replacement librarian, Ms. Crowley, whose exact role in their adventures is becoming increasingly mysterious.

After an unexpectedly thrilling summer with his grandfather, Oregon State student Charley Sawyer is ready to catch his breath at his late parents' Oregon beach home. Hoping for some rest and relaxation, Charley is met instead by devastation: the house has been ransacked. In his inventory of the damage, Charley stumbles across the item the trespasser must have been after, the only thing that seems out of place: a mysterious key. And when he learns...