The first full-length animated Scooby-Doo adventure for the big screen is the never-before-told story of Scooby-Doo's origins and the greatest mystery in the career of Mystery Inc. The story reveals how lifelong friends Scooby and Shaggy first met and how they joined with young detectives Fred, Velma, and Daphne to form the famous Mystery Inc. Now, with hundreds of cases solved and adventures shared, Scooby and the gang face their biggest, most challenging mystery ever.