Thennindian தென்னிந்தியன் Tamil Action Movie is based on three separate incidents. The first one involves the murder of a young politician, Jaimy Padamadan, which is being investigated by Jacob Alexander (R. Sarathkumar). The murder occurs during an election season and the main suspect in the case is a local don named Paruthikkadan (Suresh Krishna). The investigation is affected due to his political influences.
The second story is about Anupama (Bhavana), an I. T. Employee. She is being followed by a group of gangsters. The story takes new turns and the mystery gets solved.
The third story is about a group of five friends, Harikrishnan (Nivin Pauly), Usman (Bhagath Manuel), Sujath (Suraj Venjaramoodu), Sooraj (Arun) and Govind (Biyon Gemini). Harikrishnan is a youth working in Gulf. He and his friends are traveling to Palai. He has a package from Gulf which he is supposed to give to another person. The story takes new turns during their journey.