A murder takes place aboard Neelagiri Express, bound to Coimbatore from Madras. Ravanan is the only passenger who is travelling with the deceased. One of Ravanan's co-passengers is a mysterious woman named Kalavathy. She takes him off the train to have food at Arakkonam Station and deliberately makes him miss the train, and then she disappears. In the meantime, a wealthy man named Sabapathy is murdered, and Ravanan becomes the prime suspect in that murder. CID Inspector Shankar is assigned the task of nabbing the murderer. He realises that Ravanan is innocent and commences the investigation. So, he sets out of solving the case with the help of Ravanan and eventually tracks down the murderer.
Neelagiri Express was released on 23 March 1968.[3]Kalki said the story looked like it lacked salt and pepper.[4] Despite this, it was a commercial success.[1]
