An agent from a distant planet has been sent to earth to ship large quantities of blood to his world, where a plague is ravaging the populace. He comes equipped with an interstellar matter transmitter, telepathic mind-control powers, and deathray-shooting eyes. Because he is also affected by the blood disease, he gains control of the town's physician and has him place a nurse at his disposal, while he collects live humans for fresh blood; but gains the nurse's suspicions, along with those of her boyfriend - a town police officer.

Jeune interne aux urgences, Margaux est à bout de souffle. Lors d’une énième nuit de garde, la jeune femme oublie malencontreusement une patiente sur un brancard. Encore sous le choc, Margaux est priée de vite reprendre son travail. C’est alors que son corps se met à transpirer du sang de façon incontrôlable. Commence alors une lutte acharnée pour rester en vie.