Hari Puttar is the story of an extraordinary boy called Hari Prasad Dhoonda (Zain Khan) or Hari Puttar, as he is fondly called. Hari is an intelligent boy of 10 yrs who has recently moved from India to the U.K. with his parents (Sarika and Zakir Khan). His father, Prof. Dhoonda is assigned to a secret project with the Defense Forces at a remote location in the U.K. and has a chip at his home which contains secret and classified information. Within a few days of their shifting to London, Hari's aunt (Lilette Dubey) and uncle D. K .(Jackie Shroff) visit them along with their own as well D. K. 's boss' children. Suddenly, the house is filled with ten kids. At this point, everything changes for Hari Puttar. He has to not only vacate his room to accommodate the girls, he is also teased and ridiculed by all the other kids for being too naïve. Hari Puttar feels unwanted and subsequently when D.K arranges for a vacation for the entire family, one night before they take off, Hari's mother sends him off to the attic bedroom as a punishment for no real fault of his. The next morning, the whole family leaves in a tearing hurry, forgetting that they have left something integral behind - Hari and his little cousin Tuk Tuk (Swini Khara). But they discover this only when they are halfway into their journey. When Hari and Tuk Tuk discover that they have the large house to themselves, they begin to enjoy the sudden freedom. In the meanwhile a famous Don , Kali Mirchi, assigns two bumbling burglars (Saurabh Shukla & Vijay Raaz) to steal the secret formula chip from Hari's house. Hari accidentally discovers the mission of the burglars and is determined to save the secret formula from these burglars. The so called naïve Hari Puttar embarks on a journey of great adventure and suddenly discovers the self-confidence, creativity and courage that he did not know he had. With support from Tuk Tuk, Hari Puttar manages to not only save the secret chip but also captures the two unsuspecting thugs. Hari's mother in the meanwhile, desperate to get back to Hari goes through her own adventure to reach back home. When she reaches she realises that her son is actually a hero.