Something is rotten in New York City in 1947. Sheila Bennet (Evelyn Keyes) may be the answer. Carrying smuggled diamonds and a disease from Cuba, she thinks she is only heartsick over her philandering boyfriend Matt Krane (Charles Korvin) who has taken up with Sheila’s sister Francie (Lola Albright). Like Typhoid Mary, Sheila has smallpox and has set off a potential pandemic to run through the Big Apple. Without knowing how deadly she has become, Sheila blithely tours the hot spots with the Public Health Department representative Dr. Ben Wood (William Bishop) in hot pursuit. The federal government also is on the search, sending Treasury Agent Johnson (Barry Kelley) to find their woman.