In Shanghai Alley, by Lemuel L. de Bra (epub/Kindle)
"Like many writers of the day, Lemuel L. de Bra had other jobs before coming to writing—most notably working as a Secret Service agent in San Francisco’s Chinatown. He knew crime and Chinese culture. So he wrote about it. A lot.
“Shanghai Alley” is a crime story involving illegal drugs in Chinatown, corrupt cops, and double-cross after double-cross!