Warning revolves around the life of Shankerji, played by veteran actor GK Pillai. After landing in Mumbai, Shankerji comes face to face with an underworld leader. After defeating the don, Shankerji takes charge of the vicinity.
Shankarji later leaves Mumbai and settles down in Kerala. After a while, two young men from Mumbai reach there in search of Shankerji. It is learnt subsequently that the two boys want to take revenge on Shankerji for killing their father. However, one of the brothers' is murdered by Shankerji's men. What happens next remains to be seen.
The rest of the star cast for Warning include Maniyan Pillai Raju, Devan, Ranjith, Rohini, Geetha Vijayan, Vidya and others. Warning is produced by Aby Christopher under the banner of St. Mary's Eye Studio.