Saajan (Irrfan Khan), a Mumbai office worker nearing retirement is delivered the wrong lunch by a dabbawala. Young housewife Ila (Nimrat Kaur) had intended it for her emotionally indifferent husband. To Saajan's surprise, the food is a vast improvement on his usual meal.

When he finds a note from Ila enclosed with another meal, he decides to write back. So begins Ritesh Batra's exquisite comedy-drama.