The storyboard can be read here but below is a synopsis.
The heroes are fleeing from bullywugs by swinging on a vine across a ravine. All jump off at the other side except for Eric who is too busy laughing at his own taunts and ends up swinging back towards the awaiting bullywugs, who jump onto his vine and clamber up towards him. Hank fires an energy arrow to sever the vine below Eric, sending the bullywugs tumbling down into the ravine. Paying more attention this time Eric jumps off on the other side and lands in some bushes where he discovers a Dungeons & Dragons ride car.
Bobby wonders if it can take them home so Hank asks Presto if he can cast a spell to get the car working again. Presto is unsure but before he can attempt anything the bullywugs swing across the ravine on vines and attack.
The heroes flee while the superstitious bullywugs vandalize the car. Freddy the dog jumps up at Eric, but his barking attracting the bullywugs, and Bobby guesses that the dog wants them to follow him. Freddy runs off deeper into the jungle and the heroes follow where they find a sobbing Terri captured by lizard men and tied to a tree.
The heroes attack with Presto conjuring a floating door to swallow up an attacking lizard man before rolling up like a roller blind and disappearing. An invisible Sheila unties Terri who then urges Diana to get away from the trees. Overhearing, Diana does so just as two lizard men jump down and accidentally concuss the two she was previously fighting. Approaching Terri she congratulates her and asks how she knew her name. Meanwhile Sheila introduces Terri to the heroes just as the bullywugs arrive and fight with the lizard men over the capture of Eric. An invisible Sheila intervenes and drags Eric out from the brawling monsters.
Later at night the heroes are camping out and Terri explains how she entered the Realm via the Dungeons & Dragons ride with Freddy jumping on at the last moment, as though he knew something bad was going to happen. Terri also admits that she dreamed what was going to happen to Diana.
Dungeon Master appears and introduces himself to Terri, although she has never met him before. He tells them that there is a portal home but that they must destroy it before they leave, saying that the portal is within the Maze of Darkness and that they must first become lost to find it. He then disappears.
Shadow demon overhears and reports back to Venger, telling him about Terri.
Terri then has a precognitive dream where the portal appears on the horizon and the heroes are swept up by the wind and ferried towards it. The silhouette of Venger appears and transforms into a pyrohydra that grabs Bobby and Uni, with Bobby telling her to run. She runs and finds herself lost in the Maze of Darkness, which collapses behind her. Falling into a pit she wakes with a scream, sobbing in Bobby's arms.
Later the next day Freddy and Uni are in an idyllic valley helping Eric to find breakfast when they disturb two animals that look like giant reptilian chickens. Bobby and Terri chase the creatures and ride them briefly before being thrown off, much to their amusement.
As her dream predicted the pyrohydra suddenly attacks and grabs Bobby and Uni. Terri runs at the monster and pounds her fists against its belly. Hank startles the hydra with energy arrows and makes it drop Bobby and Uni and they escape behind a waterfall but find they are trapped. Bobby knocks a hole through the rock, which collapses the waterfall and sweeps the pursuing hydra away, and they emerge on the other side through a tunnel.
A nightmare-mounted Venger stands by the waterfall's river and muses that he wants Terri's precognitive power.
The heroes are trekking through a plain with glassy, razor-sharp rocks when the silhouette of Venger appears, as in Terri's dream, and swirls around becoming a wind that shatters the rocks into lethal shrapnel. Freddy leads the heroes out of the cutting maelstrom and into the Maze of Darkness, through an open door that they close behind them.
Terri recognises the maze as the one from her dream and that the ziggurat-mounted portal in the middle takes them back to the theme park. Eric doubts that they'll navigate the maze without getting lost and goes to leave but the door is suddenly welded shut by Venger.
Navigating the maze the heroes encounter a pitfall trap with Presto commenting that it was the third trap in the last two hours. Later on shifting walls try to seal them in but they dodge these too and find themselves among an army who seem to have died fighting each other. Suddenly the light changes and the heroes argue among themselves. Only Uni seems unaffected. Hank then realises that something is wrong and fires a flare into the air, changing the light and releasing them all from its hypnotic effects. Eric picks up a discarded helmet and the eye holes glow green and a phantom voice issues the warning, "Beware, Cavalier!"
Further on in the maze Eric makes a lasso from an energy arrow and climbs the high, spiked walls to get bearings, reporting that they are close to the ziggurat. Exhausted, the others have fallen asleep so he joins them and Terri has another precognitive dream in where she is leaving class and is greeted by Bobby who returns her locket to her. She runs to him and they embrace.
Waking, the heroes find Dungeon Master who tells Terri that the dream will come true. He then tells them that Venger built the maze over a thousand years ago and that it has been luring travellers with the promise home ever since, adding that none have survived the maze's traps and that the army were once pupils of his. Dungeon Master then disappears and the maze walls groan and begin collapsing. Remembering her dream at the camp site, Terri guides the heroes through the maze where they arrive at the ziggurat only to find Venger waiting for them.
Venger explains that they heroes are free to return home but in exchange for Terri. They refuse and he transforms into a monster and the heroes battle them, with Presto conjuring a load of mousetraps that snap on the monster's tail, while Bobby, Uni, Terri and Freddy run up the ziggurat towards the portal.
Terri hands Bobby her locket and goes through the portal with her dog Freddy but Bobby stays behind to help put the maze out of commission. Running back down to the others he is hurled by Diana towards Eric who bats him with his shield towards the ziggurat, striking it full on with his club. The portal explodes, destroying the ziggurat and maze too.
Later in a desert Bobby is lovesick and missing Terri. Despondent, he is about to hurl the locket away when Dungeon Master appears and tells him the dream she had about Bobby returning the locket to her. Elated, he rejoins the heroes who are bemused by his sudden change in mood.