Ek Din Achanak is based on a Bengali story titled Beej. The movie is directed by veteran Mrinal Sen and has won a lot of awards national and international awards.
One rainy day, when the streets of Kolkatta are flooded, Shashank, a retired professor steps out of his middle class house for a walk and does not return. His family tensely wait for him to return and start the process of tracing him after a day or so, by contacting hospitals, informing the police, enquiring with acquaintances, and so on. Days stretch into weeks, and weeks turn into months, and there is no sign of the professor. Why/ how did the professor vanish one day, suddenly? Do they eventually find him? Is he dead? Does the family finally reconcile with the situation?