In this Italian mystery-adventure, a government agent is assigned to look into a mysterious outbreak of a deadly virus in Southeast Asia. While attending a party, he meets an enemy agent and his pretty sister. Later the enemy captures the agent and his own sister who has fallen for the American. Soon the Yankee operative discovers that the evil agent is planning the genocide of all races he deems inferior. In their place, he is trying to engineer a race of superhumans. Fortunately, the American and the sister escape. He eventually finds the lab where the virus is cultivated and is again captured. This time, the sister and her friend save him and set the lab afire. The woman's friend is killed. Later her brother accidently falls into a pit filled with infected rats.