The Lurker in the Dark — J. Scot Witty

Set in the jazz age of the late 1920's, private detective, Maurice Landgrave, is accused of killing his friend and partner, David Archer. With only three weeks before his trial, he and budding detective Emmeline Quinn must navigate through the plots, intrigue, and conspiracies of international thieves, occultists, gangsters, and modern-day robber barons as they follow the footsteps last case of their dead friend in order to discover who the true murderer is. As they dig deeper into the madness, things go awry; their only refuge is with members of the underworld while even the police are hot on their trail. With so many suspects and so little time, their only hope is to solve an ancient mystery before time runs out.