Gulmohar revolves around Induchoodan (Ranjith), a school headmaster and a confirmed Maoist with a revolutionary past. He is totally different from other teachers in the school. One day, he unexpectedly meets his old friend Harikrishnan (Siddique), who is suffering from cancer. After this meet, Induchoodan's memories go back to the golden days of his past when he was a young guest lecturer at a college.
Induchoodan, Harikrishnan and a group of friends were members of the Naxalite movement. Ignited by revolutionary ideologies, they set out to fight against all social evils: corruption, injustice and exploitation. Eventually, they were arrested and subjected to cruel treatment by the police, after an unsuccessful 'Operation April' in which they targeted a cruel landlord but killed another person by mistake. Gulmohar later develops around the terrifying memories of the murder and its consequences.
With his macho look and mannerisms, Ranjith has performed convincingly as Induchoodan and deserves appreciation. His performance as an ideologist is inspiring and he has an amazing screen presence.