Kevin Flynn is a leading software engineer, formerly employed by the computer corporation ENCOM, who now runs a video game arcade and attempts to hack into ENCOM's mainframe system. However, ENCOM's Master Control Program (MCP) halts his progress. Within ENCOM, programmer Alan Bradley and his girlfriend, engineer Lora Baines, discover that the MCP has closed off their access to projects. When Alan confronts the senior executive vice president, Ed Dillinger, Dillinger claims that the security measures are an effort to stop outside hacking attempts. However, when Dillinger privately questions the MCP through his computerized desk, he realizes the MCP has expanded into a powerful virtual intelligence and has become power-hungry, illegally appropriating personal, business, and government programs to increase its own capabilities. The MCP blackmails Dillinger with information about his plagiarizing Flynn's games if he does not comply with its directives.