A man named Patrick Ross becomes the first man on Mars. But on his way back to Earth, alien DNA from the soil samples seeps out and takes over his body. Back on Earth, after having sex with female debutantes, tentacles suddenly emerge from his back, but once the women find out, it is too late. They've already been impregnated with half-alien children, and suffer explosive 30-second pregnancies in which their stomachs swell up then split open, thus giving birth to two half-alien children (and killing the female host) in the process. Soon, the same thing happens to other women as Patrick goes around raping them, impregnating them, and hiding his kids in his old childhood shed.