Robot is a science fiction action drama. The movie revolves around Vaseegaran (Rajnikanth), an excellent scientist, who was able to build a unique humanoid robot Chitti (also played by Rajnikanth) after years of hard work and research. Chitti is programmed to protect mankind and has the ability to feel human emotions. However, things take a turn when Chitti falls in love with Vaseegaran’s girlfriend, Sana (Aishwarya Rai Bachchan), and becomes obsessed with her. On knowing this Vaseegaran changes Chitti’s programming but to the former's surprise, Chitti once again transforms himself and this time to terminate Vaseegaran to get Sana into his life. Is Chitti successful in doing so, who is behind this transformation is revealed in the latter part of the story?