The First Law of Robotics staes that a robot may not injure a human being, or through inaction, allow a human to come to harm

At a crucial conference uniting the Spacers, the Settlers, and representatives of Earth, Senator Clar Eliton of Earth and Senior Space Ambassador Galiel Humadros of Aurora are advocating the restoration of positronic robots on Earth, repudiating years of fear and resentment. It is a dangerous stance to take.

As the Spacer delegates arrive on Earth, conspiritors assassinate Senator Eliton. Ambassador Humadros is cut down, too. Both are failed by their robot protectors.

Special Agent Mia Daventri - part of the security force assigned to protect Eliton - is the only member of her team to survive the attack, and is rushed to the hospital.

Derec Avery - a survivor of the Robot City epic - is called in to investigate what may have caused the robot bodyguards to fail at the most critical hour. But his inquiries are stone-walled, and an attempt is made on Mia's life. Derec and Mia join forces with Calvin Institute attache Ariel Burgess to penetrate a vast conspiracy that sprawls across Terran, Spacer and Settler worlds and threatens to bring all three to the brink of war.