Four decades ago, tragedy shook Paradigm City and wiped out memories, leaving behind mere glimpses of the past. The metropolis is still cloaked in a puzzling fog, but a select group of individuals, including the adept negotiator and agent garbed in black, Roger Smith, work tirelessly to unravel the truth. Although he never aimed to be a hero, Roger is often thrust into the role of savior, risking everything to safeguard Paradigm City and reveal its secrets. His loyal and accomplished butler, Norman, and the sharp-witted and fascinating robot, Dorothy, join Roger in navigating the murky mysteries of the city. Together, they unleash their unique brand of justice upon the criminal underworld with the aid of their colossal mecha, Big O. As Roger probes deeper into the city's secrets, he uncovers that not everything is as it seems. Nevertheless, with his team's support and the might of Big O, he forges ahead to unravel what truly transpired four decades ago and retrieve the city's former glory.