athiresan aka Kaththi, a criminal, escapes from the Kolkata prison and comes to Chennai, where he comes across his doppelganger Jeevanandham, fighting for his life after being shot at by unknown men. Kathir decides to pass off as Jeeva and make away with a lump sum amount but once he realizes who Jeeva really is, Kathir turns a crusader.

Overview from themoviedb.org