Canadian-born director Mehta shows a keen eye for the mean streets of his ancestral homeland in this small, heartfelt story of a man's search for his missing son.
The father is Mahendra (Tailang), whose itinerant work repairing zips for a few rupees barely keeps his wife, Suman (Chatterjee) and two children in their one-room slum shack.
The son is the title's Siddharth - Siddhu to his family - a 12-year-old sent to work in the Punjab factory of a distant relative (Srivasta).
When Siddhu does not return for Diwali, Mahendra is told he has absconded, but soon he is dealing with the possibility of a much darker truth. One character will tell him, "missing children are big business".
As Mahendra spends money he does not have and time he cannot afford on his quest, the mystery unfolds alongside the story of a man struggling to deal with the endless, intimidating complexity of the teeming world beyond his tiny neighbourhood.