In Paradise Island, Daphne Blakey and Velma Dinkley are taking part in an Amazon Kanga-riding training session. Nonetheless they prefer to stand back and watch while Wonder Woman takes on ten Amazons at the same time and wins.
The training over, Wonder Woman explains why she invited Mystery, Inc. over. Strange things have been happening in the island lately. Her explanation is cut off abruptly when a giant Minotaur shows up.
Meanwhile, Fred, Shaggy and Scooby are waiting in Wonder Woman’s Invisible Plane. Under Aphrodite’s law, men can’t set foot in the island or the Amazons will lose their powers and immortality. Aphrodite said nothing regarding male dogs, though, so Shaggy suggests Scooby to go and check on their female partners.
Scooby makes it to the training grounds to see Vilma, Daphne and the Amazons attacked by a rampaging Minotaur. Suddenly, the monster vanishes. Wonder Woman explains this is the fourth time in a row that ancient myth monsters appear, attack and disappear without a trace. Moreover, Queen Hippolyta has just asked her gods, and they confirmed the Minotaur remains trapped in its labyrinth.
Given the absence of crime in Paradise Island, the Amazons have no detectives to solve that mystery. Wonder Woman asked Batman to come over but being male he can’t set foot in the island, and he recommended Mystery, Inc. due to their greater expertise in supernatural cases. Daphne, Vilma and even Scooby are flabbergasted at being recommended by the world’s greatest detective, but think it’ll be hard solving this case without their male partners setting traps, running around in fear or smashing into things. Queen Hippolyta is shocked at their methods, but Vilma assures they are surprisingly effective, and suggests head back to the plane and compare notes with the guys.
The group is in the middle of discussing the case as keeping Shaggy’s fear down when they are attacked by an enormous cyclops.
The cyclops chases after the girls and Scooby-Doo, who jumps in the plane and shoves Fred into the cockpit. Fred just warns Shaggy against running outside, and his friend stammers he’d fly if he could. Suddenly, the invisible plane takes off.
Meanwhile, the Amazons are struggling to trip the cyclops. Their efforts succeed thanks to Diana’s invisible plane smacking the cyclops on his eye by accident. Once the giant is down, Wonder Woman takes off to help the guys to get her plane under control. She explains her jet is mind-controlled -which is because it flew off earlier-, and the guys manage to get the plane down… safely.
Down on Earth, the monster has vanished without a trace again. Shaggy gets panicked and wants to run out of there. Wonder Woman lends him and Fred Jumpa and a second Kanga so they can get around without touching the ground.
All of sudden, a five-headed hydra appears, and Jumpa takes off. Unfortunately, Shaggy can’t keep himself steady and falls off and on the ground.
The Hydra vanishes and the Duke of Deception appears, declaring victory is his at last. Since he couldn’t overcome Wonder Woman’s abilities, he thought of exploiting the Aprhodite’s law to take them away. Still he needed to get a mortal man set foot in the island, so he fashioned magical illusions, hoping Wonder Woman call Batman to look into the mystery. He didn’t expect them bring those meddling kids in, but they served just as well. And now he gives the Amazons permission to bow to him.
Wonder Woman shakes him around a bit before throwing him away.
As he’s wondering why his plan failed, Daphne points Shaggy’s feet didn’t actually touch the ground.
Later, Vilma and Daphne are named honorary Amazons by Queen Hippolyta and Princess Diana. Hippolyta also remarks their male companions are also worthy, and Scooby-Doo… well, he has the heart of a Kanga.