The Indigo Child is a "perfectly pure soul, never before incarnated" who holds the secret to the meaning of life. Her coming has been anticipated since the beginning of time, and numerous factions are competing to gain possession of her, as the person who hears her secret will wield control of the entire universe. In reality, her name is Jade; her parents are deceased, she is severely autistic (to the point that she does not speak), and resides in a Catholic orphanage. Her physical condition deteriorates as the cold increases, and ultimately she wastes away and dies as she reveals her secret.
Source: Wikipedia, "[en.wikipedia.org/wiki/Fahrenheit_%282005_video_game%29%23Plot Fahrenheit (2005 video game)]", available under the CC-BY-SA License.