Saravanan & Magizhnila, in love but financially unstable, see hope when Magizhnila lands a better job in a new town. However, her path soon fills with unexpected struggles. Her journey through these challenges is the essence of the story.

Sub-Inspector Vishnu and his constables arrest Saba for being drunk and creating public nuisance. They release another man, who is heartbroken. Saba tries to regain his composure by sharing his heartbreak stories.

For every action, there is an equal and opposite reaction. What happens when your small action affects so many people's lives? how the butterfly effect plays an important part in all our actions forms the crux of N4.