Karungali story is set on the backdrop of Chennai slums and here lives Ravi (kalanjiyam) who grows up selling drugs. One day, while escaping from the cops, he chances upon Dr Kanimozhi (sunitha) and he saves her from an accident.
She is impressed and decides to marry Ravi. However, Kanimozhi knows Ravi's past but is sure that she can change him. But Ravi has other plans. In between comes Amudhanila (anjali), a patient of Kanimozhi desperate to have a kid. Ravi gets to know this and starts using his brain to reveal his true colours.
What happens from there forms the rest of the story.