The film begins with a wide shot of New York City as the voice of Producer Mark Hellinger introduces the story about to be told as different from any other. We are then introduced to several situations where night workers on the Grave Yard shift go through their mundane duties. A Radio Disc Jockey is shown spinning a record, wondering to himself in voice over if anyone is listening; a woman is shown washing the floors of an office building and in voice over muttering to herself. We move silently into the window of an apartment building and we see two men wrestling with another figure as we hear the men plan how to put the body in the bath tub, and the voice over explains that this is part of the city as well- a murder is being committed. Later we see the murderers sitting by a dock as one bemoans that he never killed anyone before as his partner hits him over the head and tosses the body into the water. We are then introduced to Barry Fitzgerald as Detective Lt. Dan Muldoon in his kitchen cooking an egg for breakfast and singing an Irish folk song. As Detective Lt. Dan Muldoon goes through his administrative activities at the police station he learns that Jean Dexter a young model has been discovered drowned in her bath tub in her Manhattan apartment, and he and a young novice Detective James Halloran (Don Taylor) report to the scene of the crime. Muldoon and Halloran as well as other detectives discover a shadowy lifestyle that the young model led, and many questions are raised such as how a woman with a minimal income came by the nice apartment and jewelry that she sported, and who killed her- an ex-lover, a burglar? As the detectives look back over the months leading up to Jean Dexters murder they come in contact with Philip Henderson a supposedly romantic connection, and with Frank Niles (Howard Duff), a slippery supposed Ivy Leaguer who seemingly cannot tell the truth. Muldoon demonstrates that Jean Dexter was killed by at least two men, one who held her and the other who put a cloth with chloroform over her mouth to render her unconscious before she was put into a filled bath tub. A closer look at the jewelry of the murdered woman uncovers the fact that she was the recipient of stolen goods, and it appears that Frank Niles himself had given her much of it and also has a good amount of hot loot in his possession. When Muldoon and Halloran go to question Niles at his apartment they interrupt one of the murderers as he is attempting to dispatch Niles. Muldoon and Halloran have a new suspect as they take Niles into custody and begin pumping more information from him about his activities and how he has come into possession of all the jewelry, and they also begin tracking down his possible accomplice, the man who tried to kill him. During their investigation which includes much paper work, leg work, and specific questioning of suspects and peripheral contacts, Muldoon and Halloran and their team of detectives build a case based on the facts that an involved criminal process was in operation that dealt in stolen jewelry. Muldoon and Halloran track down all the leaders and the final accomplice leads them on a chase through lower Manhattan onto the Williamsburg Bridge as a shoot out ensues in a dramatic climax to this sordid tale.