Marvin (Marv) Frontier, eighteen, a housebound hemophiliac of the worst sort, lives a lonely existence in Tacoma, Washington. He spends his hours reading and computer surfing until one day when he is contacted by someone who calls herself Sara.

Sara assures Marv that she means him no harm, and then she reveals that she lives far away—over twenty-thousand miles away—straight up.

Sara is a satellite with a sentient computer program aboard, but she needs one more bit of code to complete her. That means Marv has to help her track down her creator, Leonard Tilderman, formerly a professor and then an employee at NASA. He's gone off the grid and no one can find him.

As Marv searches and learns more about Sara, he also finds himself falling for her, which seems to be an impossible relationship. Oddly enough, Sara shows the same amount of interest in him, and their friendship ripens into love.

Eventually, Marv manages to get the missing bit of code from the professor, just before he's killed in an accident. Marv inputs it, but NASA's representative, Major Grayson, also has plans for Sara, and Marv finds himself on the run from the major.

Things come to a head when Sara holds the world hostage by controlling every satellite still functioning, including the secret orbital weapon's platforms that NASA and the other countries possess.

Marv is eventually captured by Grayson and tortured, and his only hope is that Sara will be able to continue her journey, whether he lives or not.