The Adventure of Sherlock Holmes' Smarter Brother (1975) on Netflix

In 1891, Queen Victoria has handed over an important document to her Foreign Secretary, Lord Redcliff. The document is soon stolen from his safe. The document getting into the wrong hands could mean the start of war. As such, Queen Victoria personally contacts Sherlock Holmes to recover the document. Knowing exactly what he is doing concerning recovery of the document, Sherlock passes along one of his lesser cases to his younger brother, Sigerson Holmes, who detests his older brother as he believes he is much smarter than his more famous sibling. Regardless, Sigerson takes that case of a woman calling herself Bessie Bellwood, a music hall performer who is being blackmailed. By Sigerson's side is his new assistant, a Scotland Yard records clerk named Orville Stanley Sacker, who has a unique set of talents. Sigerson and Orville's investigation gets them into one predicament after another as they learn the true identity of their client, who has a connection to an opera singer named Eduardo Gambetti, to Lord Redcliff himself, and through association to Professor Moriarty - Sherlock Holmes' arch enemy - who is trying to recovery the Redcliff document himself to sell to the highest bidder.