The Killer That Stalked New York

Sheila Bennet arrives at Penn Station in New York after a Cuba trip, with diamonds hidden for smuggling. Realizing she is being tailed by a Treasury agent, she mails the gems to her husband Matt Krane and makes a break to shake the pursuer.

With the package on its way, Sheila continues to elude the agent through the streets, trying to lose the tail and stay a step ahead of law enforcement. The act of mailing the diamonds marks a turning point in her plan to disappear.

Feeling sick, Sheila is taken to a local clinic where she nearly faints. In the confusion she unknowingly exposes a little girl to a disease, though Sheila is misdiagnosed as having a common cold.

The little girl Sheila met is admitted to hospital and tests reveal smallpox, signaling a potential city-wide outbreak. This raises stakes for everyone involved as health officials scramble to respond.

Matt Krane has been cheating on Sheila with her sister Francie. When the diamonds arrive by mail, he tries to flee with them, but the fence cannot buy the stones because the police are actively searching for them, leaving him stuck in New York for ten days waiting for cash.

Sheila confronts Francie about the betrayal; Francie, overwhelmed by Matt's duplicity, kills herself. The tragedy fuels Sheila's desire for revenge against Matt.

Officials begin vaccinating New Yorkers to curb the outbreak, but the city rapidly exhausts its serum supply. The shortage triggers panic and complicates the pursuit of the smuggler and the disease's spread.

As cases rise, agents track the victims and deduce that the disease carrier and the diamond smuggler are one person: Sheila.

Sheila returns to the clinic seeking more medicine. The doctor explains her illness and urges surrender, but she shoots him in the arm and escapes.

Sheila finally catches up with Matt, who tries to escape from the police but falls from a building ledge to his death. The fall marks a turning point in the pursuit, but Sheila remains pursued as her illness worsens.

In the film's closing moments, Sheila nearly leaps from the ledge but is informed that the little girl she met has died. She then turns herself in to authorities and, after contracting the disease, succumbs while providing information about those she contacted.