The New Scooby-Doo Mysteries - Season 1 - Eps 21: Sherlock Doo Part 1
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.
About The New Scooby-Doo Mysteries

Title: The New Scooby-Doo Mysteries
First Air Date: 1984-09-08
Last Air Date: 1984-12-01
Status: Ended
Rating: 8.5/10 (from 100 votes)
Language: EN
Seasons: 1
Total Episodes: 26
Network: ABC
Genres: Animation, Family, Comedy, Kids, Mystery
Production Companies: Hanna-Barbera Productions
Synopsis
Picking up where 'The New Scooby and Scappy Doo Show' left off. The main difference being that the team is now occasionally joined by Daphne Blake and friends to solve mysteries together.
Cast

Casey Kasem
Shaggy Rogers (voice)

Heather North
Daphne Blake (voice)

Don Messick
Scooby-Doo / Scrappy-Doo (voice)

Frank Welker
Fred Jones (voice)

Marla Frumkin
Velma Dinkley (voice)