Zenith Brown & David Frome 
The Man from Scotland Yard [EPUB ebook] 

He was no ordinary money-lender. Among his clients were the most distinguished deadbeats in London, and he knew enough backstairs gossip to demolish the entire British peerags. One day he died—at the hands of a killer unknown. That person could be a Lord, a Lady, or a tycoon. It is up to Mr. Pinkerton to find the murderer…before the murderer finds Mr. Pinkerson!

‚Mr. Pinkerton is up to his eyeglasses in double-dealing—and triple murder. Exciting.‘ —Saturday Review