Un giovane scrittore sfortunato è sospettato di aver ucciso un vecchio banco dei pegni

However, it is later discovered that the pawnbroker had in his hands an amazing South African diamond valued over £80,000, which is now missing. Melky Rubenstein is tasked with solving the puzzle and proving the young man's innocence. 

An assemblage of mean streets lies on the southern edge of the populous parish of Paddington, in a parallelogram bounded by Oxford and Cambridge Terrace on the south, Praed Street on the north, Edgware Road on the east, and Spring Street on the west, in a parallelogram bounded by Oxford and Cambridge Terrace on the south, Praed Street on the north, and Edgware Road on the east and Spring Street on the west. The attentive will always find all the signs of gloomy semi-poverty that are more visible in London than in any other English metropolis in these streets.