Edgar Wallace 
The Melody of Death [EPUB ebook] 

ON the night of May 27, 1911, the office of Gilderheim, Pascoe and Company, diamond merchants, of Little Hatton Garden, presented no unusual appearance to the patrolling constable who examined the lock and tried the door in the ordinary course of his duty. Until nine o’clock in the evening the office had been occupied by Mr. Gilderheim and his head clerk, and a plain-clothes officer, whose duty was to inquire into unusual happenings, had deemed that the light in the window on the first floor fell within his scope, and had gone up to discover the reason for its appearance. The 27th was a Saturday, and it is usual for the offices in Hatton Garden to be clear of clerks and their principals by three at the latest.