Watch The Adventure of Sherlock Holmes' Smarter Brother

In The Adventure of Sherlock Holmes' Smarter Brother, Gene Wilder portrays Sigerson Holmes, the younger and lesser-known brother of the legendary Sherlock Holmes. He's a detective in his own right, but not nearly as famous as his older sibling. The movie is set in 1891, and begins with Sigerson attending the opera with his friend, the Scotland Yard inspector, Lestrade (played by Roy Kinnear).

After the performance, Lestrade says he has to leave to investigate a case, but Sigerson declines to join him, citing a lack of interest in the case. It's then that Madame Petrova (Dom DeLuise) approaches Sigerson, and asks for his help in recovering some letters that were sent to her by a former paramour, who she is now feuding with. At first, Sigerson is reluctant to take the case, as he doesn't see the importance of a personal squabble between lovers. However, after Petrova tells him that the letters themselves contain secrets that could damage the reputation of several prominent figures in London society, Sigerson agrees to take the case.

Soon, he discovers that the letters have been stolen by a master criminal named Moriarty (Leo McKern), and sets out to recover them. Moriarty, meanwhile, has his own agenda, which involves stealing a valuable gemstone called the Blue Carbuncle. Sigerson's investigation eventually leads him into contact with several unusual characters, including a hypnotist named Brunton (played by the great character actor, John Le Mesurier), and a woman named Jenny (played by Madeline Kahn), who has a photographic memory but suffers from chronic hiccups.

Marty Feldman takes on the role of Sigerson's sidekick, Orville Sacker, who is not quite as adept at detective work as Sigerson, but is nevertheless very loyal and eager to please. He and Sigerson manage to track down Moriarty's henchmen, including a thug known as Spike (played by Jack Gilford), and a professional pickpocket named Goldie (played by Ann Way). In one memorable scene, Sigerson and Orville have to infiltrate a criminal lair by dressing as old women, and the resulting comic hijinks are hilarious.

Meanwhile, Moriarty himself is also trying to get his hands on the Blue Carbuncle, which is being kept under heavy guard by a wealthy society hostess named Miss Kilgour (played by veteran actress Athene Seyler). Moriarty's attempts to get the gemstone culminate in a crazy chase through the streets of London, with Sigerson and Orville in hot pursuit. Along the way, they encounter several obstacles and distractions, including a group of street musicians, a group of actors rehearsing a play, and even an escaped lunatic.

Eventually, Sigerson and his team manage to recover the letters and return them to Madame Petrova, who gives Sigerson a reward of 5,000 pounds. Moriarty, however, manages to escape with the Blue Carbuncle, which Orville accidentally swallowed during the chase. Despite this setback, Sigerson is content with the fact that he succeeded in his mission, and has managed to catch the eye of Jenny, with whom he shares a romantic moment at the end of the movie.

Overall, The Adventure of Sherlock Holmes' Smarter Brother is a delightful comedy that manages to blend the conventions of a Sherlock Holmes mystery with slapstick humor and zany characters. Wilder is a joy to watch in the lead role, and Kahn, Feldman, and the rest of the supporting cast are all excellent. The film is a tribute to the classic detective novels of Conan Doyle, while at the same time being a send-up of them, and as such, it delivers laughs and thrills in equal measure.