The Black Dove: A Holmes on the Range Mystery (Holmes on the Range Mysteries)

In the summer of 1893, Gustav "Old Red" Amlingmeyer and his brother Otto (a.k.a. "Big Red") find themselves down and out in San Francisco. Though cowpokes by training, the brothers are devotees of the late, great Sherlock Holmes and his trademark method of "deducifying." But when they set out to land jobs as professional detectives, they land themselves in hot water, instead.

First their friend Dr. Chan mysteriously takes a potshot at them, fatally wounding Big Red's new hat. Then a secretive young woman from their past pops up and convinces them that Chan's in trouble -- and they're just the men to get him out of it. Unfortunately, they're too late: By the time they track Chan down again, he's dead. The police call it a suicide. Old Red calls that a lie. When he and his brother set out to prove it, they put themselves on a collision course with shady S.F.P.D. cops, brutal Barbary Coast hoodlums and the deadly Chinatown tongs.
Before long, all sides are in a race to uncover the secret that could rock the city. And their only clue to what's actually going on is the enigmatic, exotic and extremely difficult to find "Black Dove."