On the morning of April 18, 1906, the great San Andreas fault shifted violently and San Francisco was rocked by a massive earthquake. The quake was followed by devastating fires that raged across the city for three days.
In this July 20, 1906 issue of Secret Service, the detective team of Old and Young King Brady pursue the 'Frisco Fire Fiends in the aftermath of the San Francisco quake. The 'Fiends' are a band of thieving opium addicts who attempt to rob the rich mansions of Nob Hill and then set them ablaze in order to cover their tracks. San Francisco was closely associated with the opium trade in many Secret Service stories. Plots typically are set in Chinatown, with the Bradys pursuing Chinese drug lords and rescuing Caucasian women from Chinatown's sinister opium dens.