As a recent transfer to Old Detroit, Alex Murphy, played by Peter Weller in the first two movies, arrived in the middle of a super violent crime wave, a take over of the police force by Omni Consumer Products and a time of high tension for the police force who are on the verge of a strike. Unphased by all this, Murphy and his new partner, Anne Lewis, take to the streets and continue to uphold the law. However, in he middle of a coffee break, they get a call to a robbery involving an armored car in the local area. The duo manage to chase the thugs all the way to an abandoned steel mill which is in fact the gangs hideout. When inside, Murphy and Lewis split up. With Lewis quickly getting knocked out by Joe Cox, Murphy is soon outnumbered when he tries to arrest Emil Antonowsky and becomes a victim of the sadistic Clarence Boddicker who kills Murphy by blowing off his right hand, having his gang unload several clips of machine gun ammunition into him and then finally shooting him point blank in the head.
Murphy's body is taken in by the OCP and used as the prototype in their 'RoboCop' project and so, several months later, Murphy is reborn as the titular RoboCop. Originally acting as the efficient law enforcement droid the OCP were looking for, one night, RoboCop has a dream in which he remembers his death at the hands of Boddicker and his men. This awakens many memories in him from the days when he was Alex J. Murphy. First, he visits his old home to discover that his wife and son couldn't cope with his death and moved away from Old Detroit. Realising this is all due to the actions of Boddicker's gang, RoboCop goes looking for revenge. After a brief altercation with Emil, RoboCop tracks Boddicker to a drug refinery where he kills most of the people inside and arrests Boddicker who tells him that the man behind the recent crime wave is OCP's vice president, Dick Jones.
After taking Clarence back to the station, RoboCop goes to the OCP Tower to arrest Jones. However, when he arrives, he finds that he is unable to arrest Jones due to the previously classified Directive 4 which shuts him down any time he tries to arrest an OCP member. While malfunctioning, he is attacked and severely damaged by the ED-209 and the remainder of the now OCP owned police force, just about managing to escape thanks to the efforts of his old partner, Lewis. Both flee to the only safe place left in the city: The abandoned steelmill where Murphy was killed. Here, RoboCop removes his malfunctioning mask and attempts to regain some of his more human functions now that he has lost most of his robotics. Meanwhile, aware that the old partners are his biggest threat, Jones frees Boddicker, uses the police strike to release the rest of his gang from prison and gives them military grade weapons all with the purpose of hunting and killing RoboCop and Lewis.
Boddicker and his gang use RoboCop's locator chip to track him down at the old steelmill and launch an assault on him, however, they are outsmarted and quickly disposed of. During the battle, both RoboCop and Lewis became severely injured and so, with RoboCop potentially on the brink of termination, he makes one final effort to arrest Dick Jones. Storming the OCP headquarters, he enters the meeting room and displays proof of Jones' crimes to the executives in there. Panicking, Jones takes the president of OCP, known only as The Old Man, hostage and starts making demands. The Old Man fires Jones on the spot, freeing RoboCop of Directive 4 allowing him to shoot Jones, sending him crashing out of the window. Knowing his duty is done, RoboCop turns to leave the board room but is stopped by The Old Man who asks him his name. To which RoboCop responds: 'Murphy.'