Chicago Back Beat

It is Christmas morning 1933 in Chicago, and the mayor has ordered Detective Tony Alfano to take over the investigation of a messy political murder. Two bodies are in the backseat of a Ford sedan in a tony Northside neighborhood; both were shot close range in the face. The victims, a powerful alderman and close ally of the mayor, and an unidentified woman, were last seen at a Christmas Eve party at the Back Beat Nightclub. When they left, they climbed into the wrong black Cadillac limousine. The next morning, the victims are discovered miles from the nightclub, and the Cadillac and its chauffeur are missing. The mayor orders Tony to take complete control of the scene, keep the press out of it, and keep the identities secret. If asked, he is to say they are the victims of an automobile accident.
It smells like the start of a coverup, and Alfano does not do coverups.