Hari has been missing for more than seven years and Ani wanted to find him. Hari was Ani's friend from childhood; besides Ani's little sister Ashwathi's wedding was almost finalized with Hari, her cousin. So Ani sets forth to Punjab with great expectations of finding Hari.
He was not sure why Hari had to disappear especially when you know the depth of his love to Ashwathi. He found his mother in tears most of the time and watching her, he decided that he must reach Hari somehow. In Punjab, he arrives in Mallu Street and to his wonder, he locates Hari.
But Hari's name is Harinder Singh, he courts a beard and turban and his attire is purely Punjabi. Even in his behavior, Harinder Singh alias Mallu Singh looks a typical Punjabi. Ani wanted to make sure about Hari's identity and so decides to stay put for a longer period.
While contemplating the hurdles he has to overcome in a strange land to learn the truth, help arrives in the form of Karthi and Pappan. Together, the three go in search of proof to make sure that Mallu Singh is Hari. Somewhere along the line, Suseelan joins the threesome making the situation worse.
Suseelan came to Punjab to start a hair cutting saloon but on finding that no one in Punjab cuts his hair, took up cycle repair as his occupation for survival. Their probes and inquiries lead them through many adventures and they are featured very humorously in Mallu Singh.