On a tropical island, doctors are trying to eradicate malaria, a disease that is causing numerous deaths. Two of them are in love with the same woman, Virginia, a doctor. One of them, Pietro Fischer, had previously been engaged to her, but was implicated in a murder, though innocent. Having fled to avoid prison, he is tried and convicted in absentia. Years later, he returns under the alias of Dos Passos, gaining a reputation as a talented scientist.