The Dead can Tell by Helen Reilly

 Christie Lansing and Steven Hazzard are still in love after a three year separation. Three years ago, they decided to end their relationship and to go their separate ways. Steven's way led him to marry Sara who was a beautiful and ruthless woman. Now Steven and Sara were not getting along well, and Christie had come back into his life. Steven wanted a divorce from Sara, but she refused to give it to him.

On the fatal evening in this story, all the main players in this story met at a party given by Margot St. Vrain who was a successful agent for musical bands. Christie and Steven were there along with Sara Hazzard who had brought along her gun. There were notable politicians and people who were members of the New York musical and theater crowds.  When Sara Hazzard left the party, she

returned to her apartment for a short time, left it to get into her car, and drove into East River where she drowned.

This is a rather complex story which involves a group of people who are financially well off, well dressed, and prominent in the city. Inspector McKee who is head of the Manhattan Homicide Squad at first assumed that Sara's death was just an accident when he received an anonymous letter telling him that it was a murder. Then he decided to take another look at the people involved. There are brothers Clifford and Pat Somers who are in the government of New York, There is Mary Dodd who seems to be a friend to everybody, and her niece Kit Blaketon who is engaged to Clifford Somers. Oddly, Sara's maid, Eva Prentice, seemed to have disappeared the day after Sara died.

The prosaic McKee and what seems to me to be a large number of policemen who are always available to tail everybody involved in this story, and who are always at the right place at the right time, do manage to find the solution to the murder of Sara Hazzard

This book was published in 1940. Helen Reilly is noted for writing a number of police procedurals featuring Inspector McKee, and she is one of the earliest mystery novelists to emphasize the police procedural.