Naalaiya Manithan (தமிழ்: நாளைய மனிதன், English: Future Human) is a 1989 Tamil Horror - Thriller Action film was written and directed by Velu Prabhakaran. The film was produced by Thakkali Srinivasan under the banner Perfect Productions. The dialogues were written by Saveetha. Premi - Srini composed the music for the film. It stars Ajay Rathnam playing the titular role with Prabhu, Amala and Jaishankar playing the protagonist roles.The film was inspired from the American Science fiction - Horror film as Silent Rage directed by Michael Miller.
20 years into the future (2008) in Chennai, India, a doctor (Jaishankar) invents a drug which gives back life to the dead if injected within two hours of death. He works along with two other doctors Jai Ganesh and Thakkali Srinivasan. They experiment on the dead body of an orphan (Ajay Rathnam) and succeed. Unbeknownst to them, the drug induces side effects which makes the recipient immortal and at the same time alters the mental behavior of the recipient to a murdering maniac. Ajay Rathnam goes on a killing spree and the city is soon flooded with murders. But Ajay doesn't hurt the doctors as he trusts them, and returns to them every time he is wounded by bullets fired by the police.
A cop (Prabhu) starts investigating these crimes and is soon on the trail of Ajay and the doctors after suspecting their research work. When Jai Ganesh and Thakkali Srinivasan suggest to Jaishankar that they kill Ajay in order to put an end to the rampage, Ajay overhears it and later tracks down Thakkali Srinivasan, his wife (Jayashree) and Jai Ganesh, and kills them all. Later he kills Jaishankar as well.
Prabhu and his girlfriend (Amala) finally track down Ajay and after some intense bloodshed and fight, they roll him off a cliff in their car. Even after getting burnt, he comes back alive and attacks them. Finally Prabhu throws him into a deep watery pit (seemingly killing him), and leaves the place along with Amala. However, Ajay comes out from the pit, having survived.