The Killer That Stalked New York (also known as Frightened City) is a 1950 film noir starring Evelyn Keyes, Charles Korvin, Dorothy Malone. The film, shot on location and in a semi-documentary style, is about diamond smugglers who unknowingly start a smallpox outbreak in the New York City of 1947. It is based on the real threat of a smallpox epidemic in the city, as described in a story taken from a 1948 Cosmopolitan magazine article.
Wikipedia: https://en.wikipedia.org/wiki/The_Killer_That_Stalked_New_York
Suggested Film Noirs: http://bit.ly/2tLevkl
The Internet Archive is an excellent choice for entire full length Netflix & YouTube style uploads of drama, mystery, thriller & crime noir movies from the UK & USA for free. Download complete online British & American classic black & white films from the 1940s & 1950s.