Scooby-Doo! Return to Zombie Island

The gang becomes bored of mystery-solving because their villains are usually people in costumes. Daphne and Fred start a TV series focused on hunting down real ghosts, leaving the original mystery-solving team temporarily disbanded. They seek to prove the existence of genuine supernatural entities, moving away from their past antics.

Fred contacts Velma, Shaggy, and Scooby to reunite for Daphne's birthday. They plan a road trip across haunted locations in the U.S. to film Daphne's show, with the aim of encountering authentic paranormal phenomena. The reunion rekindles their teamwork and exploration of supernatural mysteries.

The gang arrives on Moonscar Island in New Orleans after being invited by Lena Dupree. The island is reputedly haunted by the ghost of pirate Morgan Moonscar. Despite their skepticism, they agree to investigate the location for their show, setting the stage for supernatural encounters.

The gang meets local residents including ferryman Jacques, Lena Dupree, who works at a mansion on the island, and Simone Lenoir, her employer. They also encounter Beau, a gardener. The characters provide background, but the gang remains cautious as strange occurrences begin happening.

Shaggy and Scooby experience a terrifying encounter with Moonscar's ghost, which turns into a zombie. The gang receives ominous warnings to leave the island, but their curiosity drives them to stay overnight. These events mark the beginning of the supernatural activity they face.

Shaggy and Scooby are chased by a horde of zombies in the night, fleeing through the mansion and surrounding area. Velma suspects Beau, but the gang quickly realizes that the zombies are real when Fred and Daphne discover one and Fred pulls its head off, confirming their fears. The situation intensifies the mystery.

While investigating, Daphne accidentally causes Fred to drop his video camera into quicksand, destroying valuable footage for their show. This setback hampers their efforts to gather concrete evidence of the supernatural, forcing them to rely on other clues moving forward.

Shaggy and Scooby find wax voodoo dolls resembling their friends and play with them, unwittingly controlling their friends' movements. Their antics disturb a bat nest, leading to further chaos. This discovery hints at the supernatural forces manipulating the events on the island.

The gang uncovers a secret passage leading to a chamber used for voodoo rituals. Velma confronts Lena, discovering she fabricated stories about the zombies. Lena, along with Simone and Jacques, reveals themselves as werecats with a dark backstory tied to the island's history of curses and supernatural revenge.

Simone and Lena recount their history as settlers cursed into immortal werecats after invoking their god to escape pirates. They reveal that every harvest moon, they lure victims to drain their life force and maintain their immortality, with Jacques helping them in exchange for his own curse of immortality.

During a ritual to drain victims' energy, the gang disrupts the ceremony, causing the werecats to surround them. The harvest moon passes, leading to the werecats disintegrating into dust and freeing the zombies' trapped souls. The gang manages to escape the collapsing supernatural trap.

Beau, who had been assisting the gang, is revealed to be an undercover police officer investigating the island's disappearances. His presence explains the safety measures and the real law enforcement interest behind the mysterious activities.

After resolving the supernatural threats, the gang departs the island. Daphne invites Beau to guest star on her show's next episode, and everyone leaves after a night of unraveling the island's haunted history, having uncovered both real and fake elements of the mystery.