( some spoiler ) sweep into new york city on a first class railroad car a killer who doesn not kill with a gun or knife or club but just with his and or it and touch and breath . a killer that a old and or even old and then man himself . that killer have a name it know the world over a smallpox . arrive in new york one cold november afternoon the killer hidden inside of sheila bennet and evelyn keyes and and like a trojen horse it wait until the opportunity present itself . then like a ticking time bomb with it fuse set off explodes throughout the length and breath of the city . sheila know that she be follow by a u. s custom officer who be on her tail since she come back to the u from the island nation of cuba . have smuggle $ 50 and 000 . 00 of illegal uncut diamond she have to be careful in get them to her husband matt and charles korvin and to be cut and sell to unsuspecting jeweler in the city . mail the diamond ahead of time sheila know that if catch the diamond would not be find on her . what she doesn not know be that matt be two time her by have an affair with her kid sister francie and lola albrght . even bad he plan to check out of town with the diamond leave her as well a francie hold the bag . even though we know right from the start of sheila deathly condition it doesn not really come to the surface until much later in the movie . the first half of the killer that stalk new york be a crime suspense or drama with the u. s custom official and nyc police look for the stolen diamond . a sheila start to get sick and begin to infect everyone whom she come in contact with the film reach the point of a mass panic in the street type horror movie . both the police and custom official together with member of the city health depertment race against the clock to find sheila before she infect the entire city of new york with the deadly smallpox infection that she carry . sheila find out from matt bos willie dennis and jim backus and that he quit his job a a nightclub piano player and that he be have an affair with francie shock her into the realization to what a heel he be . confront francie at her apartment it turn out that matt not only stiffed shelia but her sister a well . which later lead the guilt ridden francie to take her own life . on the run and not know that she infect with smallpox sheila go to her brother sid ( with bissell ) and who manage a flop house on the bowery and to find a place to stay . only too late do sheila and and sid and find out the the stolen diamond be the last of her problem . know that she die sheila go to the office of jeweler arnold moss and art smith and knowing that sleaze ball of a husband matt and who end up beat old man moss into a bloody pulp and be go to be there to exact vengeance on him . doucmentry type drama and base on a true story and with striking black and white on location photography make this movie about the horror of unseen and deadly smallpox unleash on a unsuspecting public well worth watch .