Murder on St. Nicholas Avenue - Gaslight Cozy Mystery 18

The author of Murder on Amsterdam Avenue returns to nineteenth-century New York City to find Christmas in the air, a police detective and a midwife with love in their hearts, and a wealthy newlywed with blood on her hands...
Detective Sergeant Frank Malloy and Sarah Brandt are not the only ones who have recently tied the knot. Family friend Mrs. O'Neill was delighted when her daughter Una wed the seemingly wealthy and charming Randolph Pollock. She didn't wonder why such an affluent man would want to marry a poor Irish girl, no matter how pretty she was. But now Mrs. O'Neill has a problem.
Pollock's servants have found their employer bludgeoned to death with Una cradling his body. Rendered mute by the horror of her husband's death, Una cannot explain what happened, so the police have charged her with murder and locked her away in the Tombs to await trial.
Mrs. O'Neill would like Frank to investigate the case and save Una, yet with Frank and...