To find a cure for psychopathy, scientists have created a drug that induces it in human test subjects in order to study and prevent it in the future. But one scientist's impatience leads to a terrible mistake. Ann wants out. Away from her abusive stepfather and cowardly mother, to start a new life elsewhere. And the ad she sees asking for paid volunteers to test a new drug could be the start she needs to buy new clothes, get a job and leave. And yet, one day in her basement, she finds a necklace. When she wears it, she begins to hear a voice in her head, telling her to find the owner's killer. But after testing the drug at Brimstone Laboratories, two conflicting voices in her head fight for supremacy of her self-control. One telling her to find a killer; the other telling her to kill them all. And only one of the voices can achieve its goal. Which one will it be?