Sax Rohmer 
Dope [EPUB ebook] 

Chief Inspector Red Kerry makes his debut in the non-Fu Manchu book Dope, a Story of Chinatown. Kerry is a skilled police officer who used both brains and muscle to outwit and apprehend the criminals that pose a threat to his city and its residents. He has red hair and is a strong man physically (Rohmer plays up the description more than once during the book). He tolerates very little BS, even from his fellow cops. He has the support of his superiors since he is incorruptible and produces results.
The UK did not have prohibition during the beginning of the 20th century, and people had the same glitzy lifestyle that Americans did before the Great Depression. Drugs and alcohol fueled the population growth. Kerry is attempting to uncover a mystery involving a mystic/drug dealer who becomes entangled in a web of desire and treachery.