Freddie joins Daphne, Shaggy, and the dogs in attending the Mystery Solvers Contest in London at the famous 221B Baker Street. Along with other detectives, they must solve the "Mystery of the Blue Carbuncle. Sherlock's unsolved case.
When Mystery Solvers Magazine holds it first contest in London, the gang attends along with other detectives to sold the Mystery of the Blue Carbuncle. When the ghost of Sherlock Holmes shows up, it appears he's helping the gang, but he ends up stealing security system blueprints, the gang is blamed and they must clear their names before it's too late.