2.0

Eight years after the tumultuous events of the first film, Dr. K. Vaseegaran introduces a new, sophisticated domestic humanoid android named Nila to a group of college students. During the demonstration, he reminisces about Chitti, his previous creation that he was legally forced to decommission and dismantle after it went on a catastrophic and murderous rampage. Shortly after, all mobile phones fly out of people's hands and retail outlets across Chennai, instigating widespread public panic. A high-level emergency council consisting of political leaders and scientists convenes to address the unprecedented phenomenon. Vaseegaran strongly advocates for the immediate reactivation of Chitti to combat the threat, but is vehemently opposed by council member Dhinendra Bohra, who harbors a deep personal vendetta because Chitti had killed his father, Professor Bohra, years prior.

The mobile phones coalesce into a massive swarm that brutally murders several prominent telecom moguls and corrupt officials, forcing the state's Home Minister to override objections and authorize Chitti's reactivation. A newly activated and upgraded Chitti arrives as the swarm manifests as a giant bird and wrecks havoc in the city. While fighting the bird, Chitti runs out of battery and retreats to a space research station to recharge. The swarm tries to follow but is repelled by the high-frequency positive ions streaming from the station’s broadcast antennas.

Analyzing the incident, Vaseegaran and Chitti discover that the mobile phones are bound together by a dense mass of negatively charged aura energy possessed of volatile electromagnetic properties. To exploit this vulnerability, Vaseegaran builds a high-powered photon synthesizer to stream positive ions, using which Chitti successfully neutralizes the swarm's negative charge in a subsequent confrontation, causing it to collapse. The remaining phones take the physical form of Pakshi Rajan, a deceased, eccentric ornithologist. Upon conversing with him, Chitti uncovers his tragic past.

Pakshi Rajan was a deeply passionate avian conservationist who operated a bird sanctuary from his home. He had actively protested the uncontrolled proliferation of cellular networks, demonstrating that the high-frequency electromagnetic radiation emitted from cell towers was systematically killing local bird populations. His extensive research and pleas were mocked and deliberately buried by corporate telecom giants and corrupt politicians. Driven to despair by the mass death of his avian companions, Pakshi hanged himself from a cellular tower. Later, his spirit awakened and combined with the collective life force of the deceased birds, transforming into a vengeful entity capable of telekinetically manipulating mobile phones.

Despite Chitti's appeals for peace, Pakshi remains determined to eradicating humanity to avenge his birds. Chitti successfully traps and contains the negative aura within a specialized electromagnetic containment circuit. In response to this victory, the government commissions Vaseegaran to mass-produce an army of defensive androids. However, a resentful Dhinendra sneaks into the laboratory and releases Pakshi from the containment circuit, who promptly possesses Vaseegaran's body and attacks the public again.

Chitti confronts his possessed creator but refuses to use lethal force, allowing Pakshi to violently dismantle him. To counter the threat, Nila follows Vaseegaran's encrypted commands to recover Chitti's remains and retrieve the controversial "red chip" that was responsible for his historical rampage. Reprogramming the chip with commands to target only Pakshi and no other human being, Nila reinstalls it, upgrading Chitti to version "2.0", his ruthless combat variant.

Pakshi traps thousands of people inside a sports stadium and uses nearby cell tower arrays to kill Dhinendra via concentrated radiation. Chitti and his newly manufactured robot army arrive to fight but are gradually overwhelmed by Pakshi, who uses the phones to create wings for himself and several bird drones. Before Pakshi can slaughter the hostages, Chitti deploys Kutti "3.0"—a legion of micro-sized cellular androids. The microbots latch onto all the structures made of phones and self-destruct, forcing Pakshi to stand down and allowing the hostages to escape.

Freeing an injured Vaseegaran from the lingering possession, Chitti and the remaining automated units lure Pakshi's aura back to the space station, where he is finally destroyed using the positive ions from the antennas. As Vaseegaran recovers in the hospital, he urges the state to enforce stricter environmental regulations regarding cellular radiation. Reinstated as guardians of public safety, Chitti, Nila, and their robotic counterparts depart for government service. In a post-credits scene, Vaseegaran's personal smartphone autonomously transforms into a sentient Kutti microbot, cheekily proclaiming itself to be the scientist's grandson.