context: New York City homicide detective Frank Keller is a burned-out alcoholic. His wife left him and married one of his colleagues, and he is depressed about reaching his 20th year on the police force. He is assigned to investigate the murder of a man in Manhattan, shot dead while face down in his bed, naked, listening to an old 45rpm recording of "Sea of Love". Keller has three clues â a lipstick-smeared cigarette, a want-ad that the dead man placed in a newspaper, and fingerprints of the perpetrator.
  A second man dies in the same manner in Queens. Detective Sherman Touhey from the local precinct suggests that he and Frank collaborate. Both victims had placed rhyming ads in the lonely hearts column of the newspaper, seeking dates. The detectives track down Raymond Brown, the only other man with a rhyming ad. He's a married man who admits placing the ad but swears that he threw away all the letters and never saw anyone. Frank gets an idea to place a rhyming ad in the paper, meet women who respond in a restaurant and take the prints from their drinking glasses. Frank's precinct chief is skeptical, but changes his mind when Brown turns up dead in the same manner as the other two murder victims.
  Frank has dinner with several women, while Sherman â posing as a waiter â puts their glasses into evidence bags. One woman, divorcee Helen Cruger, shows no interest in Frank and leaves without taking a drink, so Frank is unable to get her fingerprints. Frank bumps into her again at a market, but this time she is more friendly. Helen manages a chic upscale shoe store. Frank does not reveal his true occupation.
  Frank takes her to his place, against his better judgment and a warning from Sherman not to do so. They start getting passionate, but Frank panics after finding a gun in her purse and treats her roughly. It turns out to be a starting pistol. Frank apologizes, and they have sex.
  Frank and Helen begin a romance. He has a chance to obtain Helen's fingerprints on a glass but decides to wipe the glass clean. Their relationship becomes strained when she discovers that he is a cop. One night when he is drunk, he nearly gives away the fact that Helen was involved in a sting. He starts to confess his feelings for her, but then discovers that she responded to each of the victims' ads. When he confronts her, Helen refuses to admit to anything, so he throws her out.
  Moments later, the real killer bursts into the apartment: Helen's ex-husband Terry, who has been stalking Helen and murdering the men she dates. At gunpoint, he makes Frank lie on his bed and show how he made love to Helen, just as he had done to his other victims. Frank is able to overpower Terry and tries to call the police. Terry makes a lunge at him and, in the ensuing struggle, falls through the window to his death.
  Weeks later, a newly sober Frank reunites with Helen. She forgives him, and they resume their relationship.
question: Who does Frank Keller invite to dinner but who leaves before taking a drink?
answer: Helen Cruger