One day a boy named Shaggy meets a homeless puppy, to whom he gives a rather strange nickname - Scooby-doo. This becomes the beginning of not only a real friendship, but also a lot of amazing events, in which the main characters take a very active part. With the support of schoolchildren Daphne, Freddy and Velma buddies create a private detective agency, dreaming of helping the city authorities to cope with various criminals. Soon there comes a moment when the brave detectives have to face real danger: Dastardly Dick is going to release Cerberus, a creepy ghost dog, and the desperate team must stop the approaching apocalypse at any cost.