Who's Sorry Now?

This book by Jill Churchill is set during the Great Depression in a small town in New York.   All seems to be going well until an American tailor who had been raised in Germany comes to live with his granddaughter and becomes the target of race hatred.  Within days  the kindly train station porter is strangled for no apparent reason and there are no suspects.  Robert  and Lily Brewster assist the police chief in trying to solve these crimes while working to find a better way of helping the town handle the mail instead of letting everyone dig through the mail bags at the train station like they have been doing since the post office was closed.  Robert and Lily's family lost their fortune in the stock market crash but they inherited their Uncle's mansion with the stipulation they must live there 10 years and make their own spending money before they actually get his fortune.