The script can be read here but below is a synopsis.
The heroes are by a river with Bobby washing Uni. Getting splashed, Eric decides to go for a swim but a mosasaur surfaces and startles him. They think it is going to attack but instead it just swims off and the heroes deduce that it is fleeing from something.
Dungeon Master appears and tells the heroes that the Realm is in danger of destruction, and if the Realm is destroyed then the heroes will never be able to return home from it. The danger comes in the form of a demodragon, a monster that is half demon and half dragon. He then gives them a map, telling them to go to Tardos Keep and that they can defeat it by helping their adversary. Dungeon Master then disappears.
Looking at the map they see that they will have to traverse the Wondrous Wood, then the Alicorn River and then the Dustlands before reaching Tardos Keep.
The heroes find the Wondrous Wood has been burnt and the Alicorn River frozen, then hear a bestial roar (presumably from the demodragon). The trek through the Dustlands is uneventful and they come to Tardos Keep, only to find an army of orcs are planning on besieging it.
The heroes try to sneak past but Eric accidentally kicks up some dust and makes Uni sneeze, alerting the orcs and shadow demon. Instead they run towards the keep, hoping to gain entry before their pursuers catch them.
The major-domo and Queen Sulinara watch the heroes from a parapet high up in the keep and she instructs him to let them in, saying that she may learn what Venger's plan is.
The heroes reach the door, with Presto foiling his orc pursuers by conjuring marbles which they slip on, and manage to open it and enter the keep, but not before a nightmare-mounted Venger arrives, firing a mystical bolt at them.
Inside the heroes are approached by Queen Sulinara, the major-domo and some guards. She accuses them of working for Venger, saying that he has tried to trick his way into the keep before, but is pacified when she hears about Dungeon Master. Suddenly, something smashes against the door.
Outside, Venger is firing mystical bolts at the keep's door. Queen Sulinara appears at the parapet with the heroes and Venger demands the keep's treasure. She refuses saying that the keep is magically reinforced and that he will never gain entry. Venger then commands his orcs to wheel out the mystically-bound demodragon and commands it to attack. The demodragon obeys and with its alternating fire and ice breath the keep's door begins to shatter.
The heroes rush outside to attack the demodragon but although Hank manages to bind its feet with his energy arrows the monster snaps the bonds and with its tentacles plucks the totems from the heroes. Venger commands the demodragon to surrender the totems but instead it attacks him and the orc army.
The heroes rush back inside the keep where Queen Sulinara explains that their totems have interfered with the spell Venger used to control the demodragon and broken it. The monster now rampages free, unwilling to surrender the totems that allow it its freedom.
While Venger and the demodragon battle, the keep guards haul a piece of masonry over the holes in the damaged door.
Queen Sulinara escorts the heroes to the keep's gardens and explains that the treasure Venger is after is the rare herb, dragonbane, which is grown nowhere else in the Realm and that can render the mightiest dragon helpless. The heroes deduces that Venger wants it to conquer Tiamat the dragon. Presto asks why Queen Sulinara hasn't used the herb against the demodragon but she explains that the monster was created to trick her into using the herb, allowing Venger to scavenge it for his own purposes. She then reveals that the city is empty, the people having been evacuated, and that she and the others remain as volunteers to safeguard the keep and the dragonbane.
Exploring the gardens an elderly gardener beckons Uni over and gives her a garland to wear which is secretly a dragonbane wreath. When he is alone he reveals himself to be the Dungeon Master.
A gong sounds and major-domo informs everybody that the orcs are regrouping for an attack. The heroes wonder how to get their totems back from demodragon when Diana remembers what Dungeon Master said about helping the adversary, and deduces that he meant Venger.
Leaving the keep the heroes approach Venger and offer to help in defeating the demodragon. Venger conjures a talisman and tells them to aim it at the monster and speak its name. The talisman is fake and Venger is planning on sending them to their deaths.
Hank confronts the demodragon with the talisman but other than projecting a ray of light it does nothing. Realising they've been set up Eric hurls the talisman away but it chips when landing and emits a burst of light. Seeing this Hank smashes the talisman with a rock and it emits a burst of light that dazzles the monster. The heroes try to use this opportunity to reclaim their totems but Eric and Uni are grabbed by it. When the demodragon touches the dragonbane garland around Uni's neck it glows and disappears. She deduces that the garland is dragonbane and the mystery over the monster's demise is solved.
Shadow demon arrives with the orc army and demands they surrender their totems. They refuse with Eric trying to bluff that it was Presto who destroyed demodragon and that the orcs wouldn't be a match for his sorcery. Shadow demon ignores this bluff and the orcs attack but Venger intervenes and surprisingly commands shadow demon to retreat with the orcs. He then tells the heroes that as they destroyed the troublesome demodragon they are free to go with their totems but not to expect similar favours from him in the future.
The heroes head off to the keep to return the dragonbane garland and Dungeon Master watches them leave and hearing Eric mock Venger, tearfully comments that Venger was good once but everyone makes mistakes, adding that Venger was his mistake.