One Two Three’ is a story of Lost Diamonds. Batla Bhai [Manoj Punj], an underworld don’s 20 crores diamonds gets stolen by another rival don Papa’s [Mukesh Tiwari] henchman’s Albert & Pinto [Vrajesh Hirjee & Sanjay Mishra]. But they accidentally lose the diamonds to Chandu & Chandni [Upen Patel & Tanish], who works as car salesman in Laila’s [Sameera Reddy] Showroom. They hide the diamond in a petrol tank of a vintage car. Batla bhai appoints Laxmi Narayan 1 [Tusshar Kapoor], a wanna-be bhai to assassinate Papa and get the diamonds. He is asked to go to Hotel Blue Diamond, where he will get the photo and details of the target. Same time Laxmi Narayan 2 [Sunil Shetty], an workaholic, who comes to same hotel to buy the vintage car from laila for his boss. Also enters Laxmi Narayan 3 [Paresh Rawal], a small time street seller of lingerie products, who now owns a lingerie production factory. He is send by his son to select the lingerie products sample from a model cum restaurant owner Jiya [Esha Deol]. But the timing goes wrong in case of all the three. Each of them land together at the same hotel at same time. Thus due to confusion they end up getting wrong letters and photos of other person. This leads to chain of errors and confusion, which finally leads them all to the diamond.