Based on the board game of same title.
Hank, Presto, Eric, Diana, Sheila, and her younger brother Bobby all go to an amusement park one night. While there, they go on a ride called 'Dungeons and Dragons.' But while on that ride, they get sucked into the world of Dungeons and Dragons. There they are attacked by various monsters and entities. When all seems lost, they're greeted by a short, mysterious man known as Dungeon Master. He gives each one of them a magical item that they can use to fight monsters and defend themselves.
Hank (the Ranger) is given a bow that creates arrows of energy. Presto (the Magician) is given a hat of magic spells. Eric (the Cavalier) is given a shield that can deflect any attack against it. Diana (the Acrobat) is given a extendable javelin that allows her to do feats of acrobatics. Sheila (the Thief) is given a cloak that when the hood is pulled up, makes her invisible. And Bobby (the Barbarian) is given a club that can crush anything it is struck against.
They're all being pursued by the evil Venger, a man who's history is somehow tied with the Dungeon Master. His ultimate goal is to acquire all six magical items the kids possess. He has a sub-servant known as the shadow demon who spies on the kids and gives reports on their goings-on. Venger has a mortal enemy, a five-headed dragon named Tiamat. The kids are constantly looking for a way back to their home, but also go where the Dungeon Master tells them their presence is required.
The children meet a girl who has been swept into the Realm, as they have, on a rollercoaster car. The girl, Terri, has the ability to dream the future. Together they set out to find the portal home that is hidden at the end of Venger's Maze of Darkness.
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.
While resting in the Moon Forest, they're awakened during a sneak attack by Venger's Orc Army. Bobby and Hank are captured and Shiela tells everyone that she's going to follow the Orcs to see where they take them. The remaining three escape with these creatures called Cloud Bears. When Shiela searches for Hank, she's shocked to find him planning an ambush with the orc army, even saying that Venger need not worry and that everything will happen as planned. When he returns to the group, Shiela exposes him to the rest and he's branded a traitor by his friends. The truth is Hank is going along with Venger so he will not harm Bobby. If Hank so much as reveals his true cause for betrayal, he endangers Bobby's life. Caught between a rock and a hard place, Hank must still lead his non-trusting friends and help save Bobby.
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.
The children come to a cursed village in the middle of the Swamp of Darkness. Venger is using a wild talent illusionist called Varla to keep the village in a permanent state of decay. The children meet Varla's parents and have their weapons stolen by Venger, who uses Varla's powers to trick them and bring the village against them. The children set out to regain their weapons and rescue Varla from Venger's fortress.
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.