Elijah is a class five plain-clothes detective with the New York City Police Department. He lives with his wife and son in the heavily populated, enclosed City. Practical and deeply concerned with his family's security, he fears the increasing displacement of humans by machines. His pragmatic nature causes friction when he receives an assignment to work with a Spacer robot on a high-stakes murder case.

Daneel is a highly advanced humanoid robot created by Dr. Sarton, designed to be visually indistinguishable from a human. He possesses a positronic brain bound by the Laws of Robotics and operates strictly on logic and a defined sense of justice. He represents the Spacers' attempt to integrate robots into Earth society.

Jezebel is Elijah's wife and a former kitchen worker who strongly desires community connection. She dislikes the social isolation brought by her husband's police privileges. She struggles with the history of her full name and prioritizes conformity over luxury, drawn to the romantic ideas of the Medievalist movement to find belonging.

Julius is the Police Commissioner of New York City and Elijah's boss. He is a politician by nature, capable of managing people without causing resentment. He maintains a deep sense of nostalgia for Earth's past, evidenced by his unusual preference for office windows and spectacles over modern alternatives.

Dr. Fastolfe is an older Spacer scientist from Aurora with a pragmatic approach to human survival. He advocates for Earth citizens to colonize new planets using a cooperative human-robot culture. He acts as an authority figure for the Spacers on Earth and provides crucial information to the police.

Dr. Sarton is a Spacer scientist and roboticist from the planet Aurora. He traveled to Earth to study human psychology and promote the integration of robots into human society before his sudden death instigates the novel's central investigation.

Bentley is the 16-year-old son of Elijah and Jezebel. He is observant and enthusiastic, showing a keen curiosity about robots and book-films. He requires contact lenses for his vision and occasionally feels frustrated by the City's synthetic food options.

R. Sammy is a basic police department robot assigned to perform administrative tasks. His presence irritates the human staff, particularly because he replaced a human worker. He symbolizes the ongoing displacement of Earth citizens by machines.

Francis is a 35-year-old zymologist who develops yeast strains at New York City Yeast. He is a vocal participant in the Medievalist movement, expressing strong resentment toward robots due to concerns about his children's future employment.

Dr. Gerrigel is a roboticist called in to consult on the case. Like most city dwellers, he suffers from agoraphobia and strongly opposes the idea of traveling across open country, prioritizing the safety of the enclosed City.

Boris is Elijah's maternal uncle. He worked at the yeast factory during Elijah's youth and used to smuggle out small treats for him, leaving a lasting impression on his nephew.

Simpson is a police department employee who shares the general human animosity toward robotic replacements in the workforce, openly expressing a desire to harm R. Sammy.

Lizzy is a friend of Jezebel who introduces her to the Medievalist movement's meetings, providing the social connection Jezebel desperately seeks.

Gerhard is a citizen involved in the Medievalist movement and present during the unrest at the shoe counter, participating in the harassment of robots.

Prescott is a personnel employee at New York City Yeast who directs the detectives to their suspect during the investigation.

Vince is a former human employee at the police department who was declassified and replaced by R. Sammy, serving as a cautionary tale for the remaining human staff.