Scooby-Doo on Zombie Island is a 1998 animated movie that reunited the classic Mystery Gang and sent them off to Moonscar Island, a fabled place rumored to be haunted by the terrifying werecats.
The gang, consisting of Fred, Daphne, Velma, Shaggy, and of course, Scooby-Doo, have now gone their separate ways, but a TV producer offers them a chance to reunite and produce their own show. In search of a new mystery, Fred suggests that they go to Moonscar Island, after reading about it in a haunted locations guidebook.
Upon arriving on the island, they discover that the locals all believe in the existence of werecats, but the gang is skeptical and chalks it up to superstition. However, as they begin to investigate, they quickly realize that they may have been wrong. Strange things happen, like dead animals coming back to life, and the gang starts to realize that they might, in fact, be facing real supernatural forces.
The gang soon encounters a group of people who live on the island, but they are soon attacked by the werecats, who turn out to be real. They discover that the group they met is actually a pack of ghosts who are cursed to live on the island forever, with no hope of escape unless they can break the curse. The ghosts reveal that the island was once used for slavery and that many people died there in the past, leading to a curse that has turned the former slaves into immortal werecats.
The mystery of Moonscar Island is far more complicated than the gang first thought, and they are forced to fight for their lives against the supernatural creatures that inhabit the island. As things come to a head, the gang must use all their wits to unravel the mystery of the curse if they hope to escape with their lives.
In the end, they do solve the mystery, but not without learning some dark truths about the past, and finding a new respect for the supernatural forces they once thought were mere costumes. The movie ends with the gang separating once more, but as they leave the island, they know that they've faced something far more challenging than anything they've encountered before.