Martin is living with his sister Karen and finds himself one day trying on some of her clothing, unusual in that he had never felt such an urge before in his life. Martin starts acting more and more female over the next few weeks and wondering why. He has no idea that Karen has been manipulating him chemically to become her "little sister" Martina.
As he metamorphes into a beautiful young woman, Martin feels strange new urges involving attraction to men who apparently find him very attractive in return. He also becomes a defacto mother to his sister's daughter Tracie, including a new ability to breastfeed. This story takes some completely unpredictable turns that you are guaranteed to not see coming, culminating in an ending that you will not expect.