In the year 2035, humanoid robots serve humanity, and humans are protected from the robots by the Three Laws of Robotics. Del Spooner, a Chicago police detective, hates and distrusts robots because one of them rescued him from a car crash, leaving a 12-year-old girl to die because her survival was statistically less likely than his. Spooner’s critical injuries were repaired with a cybernetic left arm, lung, and ribs, personally implanted by the co-founder of U.S. Robots and Mechanical Men (USR), Dr. Alfred Lanning.
When Lanning falls to his death from his office window, the CEO of USR Lawrence Robertson declares it a suicide, but Spooner is skeptical. Spooner and robopsychologist Susan Calvin consult USR’s central artificial intelligence computer, VIKI (Virtual Interactive Kinetic Intelligence), to review security footage of Lanning’s fall. Though the video is corrupted, they learn that no other humans were in Lanning’s office at the time; but Spooner points out that Lanning could not have thrown himself through his heavy office window—only a robot could have generated the necessary force. Calvin protests that this is impossible, as no robot can violate the Three Laws, but they are then attacked in the office by an NS-5 robot, USR’s latest model, in violation of the Laws. After the police apprehend it, they discover that the robot, who tells Spooner its name is Sonny, is not an assembly-line NS-5, but a unique individual built by Lanning himself, with stronger armor protection and a secondary system that bypasses the Three Laws. Sonny also appears to have emotions and dreams.
While pursuing his investigation of Lanning’s death, Spooner is attacked by a USR demolition machine, and then a squad of NS-5 robots. His boss, Lieutenant Bergin, worried that Spooner is losing his mind, removes him from active duty. Spooner and Calvin sneak into USR headquarters and interview Sonny. He draws a sketch of a recurring dream: a leader, who Sonny believes to be Spooner, standing before a large group of robots on a hill near a broken bridge. When Robertson learns of Sonny’s immunity from the Three Laws, he orders Calvin to destroy him by injecting nanites (replicating nano-scale robots) into his positronic brain. Spooner recognizes the landscape in Sonny’s drawing as Lake Michigan, now dried-up and used as a storage area for defunct robots. Upon arriving there, he discovers NS-5 robots dismantling older models and preparing for a takeover of U.S. cities.