A young female terrorist goes on a suicide assassination mission, but her resolve to complete it is put to the test.

The prime minister of the nation gets killed and an efficient police officer, Sivaraman, gets appointed by the government to solve the murder mystery. He gets ninety days to accomplish the mission.

"Cyanide" is about the incidents that occurred in the peripheries of Bangalore after the assassins of former Prime Minister Rajiv Gandhi stepped into the city. The story revolves around a helpless couple who fall into the clutches of the gang and are taken hostage.

Ramakrishnan and Arun both are ACP’s and colleagues, Ramakrishnan fall in love with Divya, and Arun loves Geetha, these two couples get married, but due to some misunderstanding between Arun & Geetha makes them depart, in the flash back. Mean time the Rajiv Gandhi assassination was carried out by Sivarasan & co and they get hide in Bangalore. As a special officer Karthikeyan is taking in charge to find the odd peoples. With the help of two ACP’s Ramakrishnan & Arun, Karthikeyan tracking the network in Tamil Nadu, at last they able to find the Sivarasan gang hiding in Bangalore, in a successful operation Ramakrishnan tries to capture the Sivarasn allies, but unfortunately Ramakrishnan able to capture only the dead bodies of the terrorist organization. What transpires later forms the crux of the story. Based on True Events (Rajiv Gandhi's Assassination).