Vinashak is about Inspector Arjun Singhs battle against Jailor Lankeshwar, his prisoner and henchman Ashgar, and two officials in league with Jailor Lankeshwar. Lankeshwar sends Ashgar to commit crimes outside of the jail. Inspector Arjun Singh's superior, Mr. Agnihotri gets this information and contacts two officials to help destroy Lankeshwars den.
However unknown to him, the 2 officials are criminals who actually help Lankeshwar commit the crimes. Lankeshwar and the two officials make a plan to kill Mr. Agnihotri and have his death be blamed on Arjun Singh, while pretending to help them both.
Consequently and subsequently, Inspector Arjun Singh is jailed for the murder of Mr. Agnihotri and only later finds out he had been part of a conspiracy against him. Now he prepares for revenge against all four men as Vinashak.