Contagion of the Night - Edward J. Leahy

Minutes before twelve on a night in 1943, Detective Dan Brady is summoned to a churchyard where a woman has been found strangled. He soon discounts the theory that the woman was killed during a mugging, and an interview with her widowed husband yields more questions than answers.

When a man's body is found on a rocky islet a few days later, Danny connects him to the woman's murder, and soon suspects mob involvement.

As he widens his investigation to include the Bronx rackets, he encounters resistance from his lieutenant and an assistant district attorney, and is cautioned by a friend in the FBI, who nevertheless agrees to provide helpful information. As he probes deeper, he learns of the reach of organized crime in the city.

When a detective who provided him with information disappears and Danny discovers he is being followed, he realizes he is placing his fellow detectives, and possibly his wife and newborn son, at great risk.

Based on true events.