Pachamarathanalil movie begins with the happy family of the well-settled Sachi (Sreenivasan), attractive Anu (Padmapriya) and their daughter, the charming Sneha. Sachi is a successful cartoonist, whose famous creation -- 'Poompatta Princess' is admired greatly by the readers. The story moves on a fast track when Sneha is seen by ad film maker Teny at the child’s school function. Teny wants to do an ad film with Sneha. Seeing his daughter’s enthusiasm, Sachi acquiesces.
On the way to the shoot, the father suddenly finds his daughter missing and cannot find her. Enters the scene Chief Inspector Venkatachal Aiyer, played by Nasser. As investigation for missing Sneha continues, unexpected facts come to light like Sachi is not the father of Sneha. The rest of the movie solves the mystery.