Louis Tracy (1863-1928) was an English journalist and author of Science fiction. His best-known detective is Inspector Furneaux. Other books feature Reginald Brett, a barrister. Tracy also collaborated with fantasist MP Shiel on eight novels under the pseudonym Gordon Holmes. Extensive details of this collaboration can be found on Shiel's site. Some of Tracy's works can be found at Project Gutenberg.

Bibliography

The Albert Gate Mystery (1904): Being Further Adventures of Reginald Brett, Barrister Detective

Number Seventeen (1916)

The Postmaster's Daughter (1916)

The Strange Case of Mortimer Fenley (1919)

The Gleave Mystery (1926)

The Law of the Talon (1926)

The One Girl in a Million (1928) aka The Manning-Burke Murder

What Would You Have Done? (1928) aka The Sandling Case

A comprehensive Tracy bibliography can be found here, but there is no separate listing for the mystery stories.