Robot Rex is the protagonist and relates this runaway story with well- oiled efficiency. Lifetime companion to 16-year-old Paul Simpson on planet Ganymede, Rex is sold into farm labor when Paul's family returns to earth. In an effort to see Paul one last time before the rocket leaves, Rex breaks all robotic rules and runs away from his new owner. Paul, after learning of Rex's escape, abandons ship and family and they team up. From then on it's Run Robot Run as they agonizingly progress via Mars to Earth. Rex, accused of kidnapping Paul, finds himself experiencing all manner of new emotions not the least of which is worry. A hero-botic act of self sacrifice finally brings things to a satisfactory halt. Mr. del Rey has Rex under push-button control but the plot plays hopscotch on the borderline of credulity.