One night in the New Orleans slums, vicious hoodlum Blackie (Jack Palance) and his friends kill an illegal immigrant who won too much in a card game. Next morning, Dr. Clint Reed (Richard Widmark-this time not seen pushing little old ladies in wheelchairs down the stairs) of the Public Health Service confirms the dead man had pneumonic plague. To prevent a catastrophic epidemic, Clint must find and inoculate the killers and their associates, with the reluctant aid of police captain Tom Warren (Paul Douglas), despite official skepticism, and in total secrecy, lest panic empty the city. Can a doctor turn detective? He has 48 hours to try.