When a body is found in the New Orleans docks, it’s pretty obvious that he died from gun shot wounds. The police surgeon notices that the man is also displaying other symptoms and Lt. Commander Clint Reed, a doctor with the U.S. Public Health Service, diagnoses a highly contagious disease, pneumonic plague. He tries to convince local officials to find everyone who may have been in contact with the dead man. The Mayor supports his efforts but many, including the police, are doubtful. Reed wants to avoid publicity so as not to panic the public. They have little information to go on – they don’t know the dead man’s identity – and Reed estimates they have 48 hours before disease begins to spread. With police Capt. Tom Warren going through the motions, Reed sets out to find the killers.
At night, on a seedy street of New Orleans, we see an upper floor window that is thrown open. In that room a poker game is under way. One of the players is seaman Kochak (Lewis Charles), who gathers a large pot he has just won and says he feels sick and needs to go rest. The other players object, Blackie (Jack Palance), Raymond Fitch, ( Zero Mostel), and Poldi (Guy Tomajan), claiming that it was too early to quit. Despite threats, Kochak leaves. Blackie quickly talks to the other two, ordering them to bring back Kochak or the money. Raymond and Poldi follow Kochak out, stop him and push him, but Kochak continues on his way. Raymond and Poldi are giving up, but an angry Blackie demands that he be followed. Some distance away, in the dock area, Kochak is surrounded, there is a brief fight. Blackie kills Kochak with two shots and orders Raymond and Poldi to get rid of the body after retrieving the money.The next morning, Dr. Clinton Reed, a U.S. Public Health Service officer (Richard Widmark) is at home looking forward to a day off with his wife Nancy (Barbara Bel Geddes) and son Tommy (Tommy Rettig), We see him as a family man painting furniture with his young son. Later he and the wife discuss how it appears they can't make ends meet with his salary, as there are bills that have gone unpaid for quite a while.From a dock on the river front, the dead body of Kochak has been spotted, and policemen pick it up and take it to the morgue. The coroner technician digs out the two bullets and notices something strange with the body. Immediately he isolates the body and phones Dr. Reed at home.Dr. Reed reluctantly agrees to come back to the morgue, and confirms the dead man had pneumonic plague, similar to bubonic plague but attacking the lungs, and transmitted not by rats but by coughing and sneezing and physical contact among people. He takes charge, isolates everyone who touched the body, has the body cremated and starts inoculating the policemen and morgue technicians.At a hastily summoned emergency meeting with mayor Murray (H. Fowler, Jr.), police chief Tom Warren (Paul Douglas) and other authorities, Reed describes the potentially enormous consequences and deaths that could ensue from not finding those infected. Death occurs within four days of the onset of illness, and illness within about two days of contagious exposure. So they have a 48 hour window to try to find those exposed and prevent further illnesses by inoculations.Since the dead man was moved by his killers, the killers have been exposed and must be found. The search has to be done with a different excuse, otherwise the killers might leave town and potentially infect the whole nation. The secret must also be kept from the public, otherwise there would be a mass exodus that might spread the illness through a vast area.The mayor supports Reed, the rest go along very reluctantly. Warren objects that he has an impossible job because the murder victim is unidentified, but grumblingly he promises to do his best. Reed and Warren display short tempers and grudging respect for each other as they start off on their search for the killers.Warren orders a round up of all known petty criminals and suspects, who are shown a picture of the murder victim and are asked what they know. Reed is so involved an intense that he gets in the way of the police procedures, so he goes on his own to try other ways to identify the murder victim.Dr. Reed goes into the seamens hiring hall and offers a $50 reward to anyone who can identify the murder victim, to no avail. He senses there is a reluctance to give information, so he announces he will wait at a nearby café, Franks Place just in case anyone wants to talk to him. After some waiting, a girl comes to him and says she thinks she knows a boat owner who might have seen the unidentified victim. Reed follows her to a boat and the owner denies knowing anything. After some pushing, the owner says he also owns a café that is run by his wife and will ask his wife.At the café, the wife is consulted by her husband out of sight from Reed. She recognizes the man but refuses to admit it. She complains of having a headache, and she starts to cough.Meantime, Blackie, Raymond and Poldi have sensed that the police is after something important, and Blackie guesses that the dead man, who was Poldi's cousin, is much more important than one would guess from a merchant seaman, and imagine that Kochak had information about some treasure or drug stash.A scene in Blackies supposed legitimate business serves to define the characters of both Blackie and Raymond. Blackie argues with Raymond and his shrewish wife (Liswood), and shows Raymonds frantic subservience as he tries to pacify each, like some berserk pinball.There are brief scenes where Blackie's complex character is further developed. When a stunning prostitute asks Blackie for $100 (the equivalent of $1000 in 2010), he doesn't hesitate. When a little newspaper seller gives him some information, he insists on giving money to him, although, he doesn't want it. When a doctor tells him that the man he is trying to kill is sick and needs an expensive sanitarium, Blackie quickly offers the money. He may be a killer, but he sure is generous.The film intersperses small scenes that grab attention simply by making the characters and their little exchanges interesting. Like the Irish dwarf, for instance, who refuses to take payment for his favors, looking up at the towering Blackie, saying, "No, Blackie, no." And then after Blackie stuffs the bills into his sweater, he hobbles away backwards and saying, "God bless ye, Blackie, God bless ye."In the same vein, Reeds character is developed as struggles with his status as a nearly absentee dad, slaving away at a job that pays him poorly and barely managing to spend any time with his wife and son. The $50 reward he offers for information means the bill he was going to pay will have to wait.Blackie starts to suspect Poldi of holding out on him, since Kochak was Poldi's cousin, so Poldi disappears trying to get away from Blackie.Meantime, the wife of the café owner has been taken to a hospital, and dies from the plague. Her husband arrives, and Dr. Reed is able to extract more information due to the heavy guilt and grief. Kochak is identified as having arrived in a ship called the Queen of the Nile, which is still within reach of the authorities.The ship is boarded, and despite the Captains denials and lack of cooperation, Reed succeeds in questioning the crew, and finds that there had been a recent death on board. The interview of two Asian cooks aboard the Nile Queen is hilarious — "He cawr me dirty names and ask for Shishabob!" Later, loudly proclaiming that the crew will start dying in just a few days, Reed succeeds in convincing the seamen to get inoculated. The captain yields as his crew starts to mutiny.During these searches, three times, Reed just misses meeting up with Raymond. The viewer is tantalized with both men in the same frame but unaware of the connection between them.The film has a subplot in which a news reporter, who wears his "Freedom of Speech" as a badge of honour, is shut down and locked away in a jail, to prevent him from publishing a story that might indeed trigger panic in the streets. This is a decision by the mayor at the urging of Reed that gives rise to a brief discussion of Constitutional rights.Eventually Blackie finds and interrogates the dying Poldi as to the precise nature of his cousin's presumed contraband. Cat like, Blackie stalks his victim across the room, eventually preying over the doomed man's sick bed, holding Poldi's feverish head in his hands. Meantime, Poldi's mother has summoned a nurse, whose entrance prevents Blackie from torturing the dying Poldi. She is aware of the seriousness of Poldi's condition, and refuses to leave. Blackie summons his own doctor, and the doctor expels the nurse, who manages to get messages to Reed about the situation. Were it not for the serendipitous perceptive nurse, Reed and Warren might still be looking for the killers.The doctor together with Blackie Fitch start to move Poldi out of his room and down some stairs and this is when they meet up with Reed. Poldi is thrown down to his death, and an exciting chase follows. Blackie and Raymond hijack a van to flee, as they are being chased by Reed, Warren, and half the New Orleans Police, first in 1949 Ford police cars, then on foot after the van is surrounded. The two escaping killers try to throw off the pursuers in a coffee and bananas warehouse where they hide among the mountains of burlap coffee bags. At one point Reed enters and yells at them that they will die unless they surrender and get inoculated.The weight challenged Raymond trying to keep up with Blackie is a source of shots that would be funny except for the circumstances.After Raymond is captured, in the final chase shots Blackie is on the run at the water level under the wooden docks, with the police hot on his tail. Trying to escape on a fruit boat headed towards South America the dirty and murderous rat, Blackie, is prevented from getting on board by the ship's rat shield causing him to end up in the water where he is eventually captured.The final shots symbolize that the emergency is over, as the exhausted Reed returns to his family.