Touted as a cure for cancer, Dr. Alice Krippin's genetically altered measles virus catches humanity off-guard when a sudden mutation causes it to become fatal. Years later, 90% of human life on Earth has fallen prey to the virus and been transformed into primal, violent monsters that roam after dark. The sole survivor in all of New York City, virologist Robert Neville takes it upon himself to find a cure after the death of his family. He spends his days foraging for food and experimenting on the affected humans he captures. Hard work and sacrifice lead to a breakthrough, but when tragedy strikes as he finally finds his cure, he gives his life to release it to the world.