Dungeon Master sends the Young Ones to the walled city of Tardos Keep to save Queen Solinara and her people from Venger's besigement. But the evil wizard has a wicked surprise for the kids--Demodragon, a two-headed fire and ice spitting monster capable of trashing the entire Realm. Will they learn what the fabled treasure of Tardos Keep is before the out-of-control Demodragon destroys their chance to get home?

Back in the real world, a boy named Jimmy is pulled under his bed and vanishes. In the world of Dungeons and Dragons, the kids are lost. The Dungeon Master tells them they have to find the City at the Edge of Midnight, where children from this world and the theirs are being held prisoner. They then find an oasis, that's inhabited by a clan of monsters. When the monsters have them surrounded, a traveller by the name of Ramuud comes and saves them. He then leads them away from the cursed oasis to his own encampment. Ramuud then explains that long ago his daughter, Aisha, was kidnapped by the Nightwalker and is being held prisoner at the City at the Edge of Midnight. Wanting to return the favor of saving them from the monsters, the kids offer their help, but Ramuud tells them that it's not nessary. But when Bobby is kidnapped that night, they're forced to enter the City at the Edge of Midnight to fight the dreaded Nightwalker.

After an attack by a swarm of wasps, the Dungeon Master greets the kids. Eric expresses that Dungeon Master's presence is always convient for him and his power is going to waste. The Dungeon Master then explains that his job requires him to give his attention to many places that need him and that his job is never an easy one. When Eric states that if he were dungeon master it would be the easiest job in the world, the Dungeon Master takes him up on his offer. For one whole day, Eric is the Dungeon Master. His last instructions are to head to Dark Haven to seek the Golden Grimoir, which holds the key to everything they seek. When everyone starts to think Eric being the dungeon master is a bad idea, Eric promises to get everyone home once he figures out the powers of being dungeon master. Soon Venger finds out about Eric being dungeon master and begins searching for his chance to aquire the power of Dungeon Master.

After another attempt at getting home is foiled by Venger, the frustration is too much for the kids. They decide to take the fight to Venger and finish things once and for all. Their idea: Tiamat - Venger's mortal enemy. When they disregard Dungeon Master's next mission to embark on their own, he advises against it and then indicates where they can find Tiamat. A place called the Dragon's Graveyard, where old dragons go to die. The kids then start their journey to the graveyard, but not without the presence of Venger in the midsts.

The kids stumble upon a young man, sick from exhaustion and hunger. His name is Kosar and he has escaped imprisonment by a demon called Queen Seris. She wanted Kosar out of the way so she can remain in rule, fearing the 1000 year-old ancient prophecy that must be fulfilled by a 'child of the stargazer.' The legend states: And on the night of star fall, the child of the stargazer shall come from a faraway land to stand in the Temple of Light. The demon shall be vanished and the child shall journey home. After an attack to take back Kosar, the kids start their journey to the Temple of Light. But when Kosar is taken back by magical means, Diana is taken back with him. Once there, they have to fulfill the prophecy until the others catch up with them.

Eric and Bobby retrieve a box for Dungeon Master. Dispite the fact that they were under strict orders not to open it, Eric gets curious. Just as he pulls the pin from the lock, Dungeon Master appears and warns Eric to place the pin back in place before it's too late. But Eric is taken by surprise when a force blows the top of the box off and releases He Whose Name Cannot Be Spoken. He is Venger's master, pure evil, and a powerful entity. The Realm is covered in darkness and a whirlwind envelopes the land. Dungeon Master then instructs the kids to flee on foot, and he joins them. When Eric demands to know why he should follow any further, Dungeon Master simply informs him: We are running, Cavalier, for our very lives.

Venger's got a new idea for eliminating his annoying young enemies, and pulls both a futuristic plane and a WWII Nazi fighter pilot into the Realm using his Crystal of Chronos. Venger intends to send Josef Mueller, the pilot, back to Earth to win the war for Germany, but after meeting the kids, Josef has other plans.