"Yeh Sunday Kyun Aata Hai" is a film about four shoe-polish boys of Mumbai, aged between 10 and 12 years old, who carry out their work at the Goregaon Railway Station. Even though life is far from being idyllic for these four, the boys, Dholak, Master, Jhingur and Chillar are full of enthusiasm and a zest for life, with colourful dreams of a better tomorrow. Master wants to become a big business man, Dholak wants to be a famous singer, Chillar wants to become very rich by winning lottery, While Jhingur wants to become Bollywood Superstar, Hrithik Roshan. But on the other hand, they have their day-to-day problems to deal with which make their survival on the platforms very difficult.
Their meager daily earnings hardly suffice to provide them even a single square meal. They earn to Rs. 60 to Rs. 70 per day from Monday to Saturday. The larger problem and the biggest threat go by the name 'Sunday' being an official holiday for most. A day to rest for every office-goer is a day they have to forego their daily bread as these Children's earnings majority depends upon these office-goers, as they are their only regular cilents. As a result of this, on Sunday, they are unable to earn hardly any money, and their problem doesn't end here, the Railway Policemen, who take Rs. 20 to Rs. 30 everyday, as a bribe and protection money from these children, did not spare them even on Sunday. Now when these Railway Policemen do not get their share on Sunday, they make these children's life hell. That is the reason, these shoe-polish boys often say " Yeh Sunday Kyun Aata Hai?"
On one such Sunday their lives are completely shattered, when one of their friend, Dholak goes missing. Master, Jhingur and Chillar do their best to find Dholak, but they can not find him. They even approach some Ministers and Policemen, but nobody is even interested in their story, as they are not from any influential families. This one incident brings down their dreams and deals a cruel blow to their fate. Will Master, Jhingur and Chillar ever be able to find Dholak again? How do they overcome their strife and struggles? Will they ever meet someone who can represent them and help address their pathetic plight to the concerned authorities?
Who will come forward to help them? Will life ever go beyond on a Sunday?