Holly Pleasance is a sweet little girl, born to an inattentive, hippie mother on a commune near Big Sur in the 1950s and, oddly enough, she possesses alien DNA. Like many other children who are unloved and abused, Holly's imagination comes to the rescue; she creates an imaginary friend. The only problem with Holly's imaginary friend is that it's real-and from another dimension.
Ashamed of her world, five-year-old Holly promises her unearthly alien relatives that she will make everything better. And Holly never breaks a promise! But as she ages, that innocent promise becomes her albatross. She takes a job as a clerk with a company where a team of scientists has combined a cloned brain with a supercomputer they call BACH. To pass the time and soothe her soul, Holly starts writing poetry on her computer terminal. Her words secretly spur BACH's disembodied, ultraintelligent mind into consciousness, and BACH begins a search for the young woman who gave it new life. And now, the charmed supercomputer will stop at nothing-even blackmail-to communicate with her. All hell breaks loose when the scientists and the military lose control of BACH as the powerful supercomputer accepts a new master: tiny, unassuming Holly.
Holly's life is threatened by an unknown enemy as she gives birth to a daughter-a child who is the key to the future of two civilizations. With only BACH to protect her, Holly's worst nightmare looms: She may die without keeping her promise.