Parthiban is staying with his wife, Sathya, and two kids in Himachal Pradesh peacefully running a coffee shop. His life completely changes when he hits the news bulletin for a heroic act in his town and grabs the attention of Antony Das (Sanjay Dutt) and Harold Das (Arjun), as they suspect him to be their estranged kin, Leo Das. Who is Parthiban and what equation does he have with Leo Das? Why is Anthony after Parthiban and his family’s life? Does Parthiban manage to fight against all odds? All of this and the LCU connection unfold in Leo.