Sunderdas was a perfectionist - if he waited fifteen years to strike, it was with the knowledge that fifteen years was long enough for parents to accept anyone with a striking resemblance as their long lost son. Sunderdas had been fortunate to come across Shanker, a pavement dweller who took life just as it came to him. Shanker fell a ready prey to Sunderdas's slick talk, and was a willing tool in the hands of a cunning craftsman.
Shanker duly appeared at Dwrkadas's residence in the guise of their son, Kundan, lost fifteen years ago. To the aging and pining parents, Kundan he surely was! And if Vijaya, Kundan's younger sister and her suspicions, she could not accuse with certainly, nor was she eager to break her parents' hearts after fifteen long years of unhappiness.
Kundan, as he now was, met the beautiful Meera, and a fairy-tale romance blossomed between the millionaire's son and the poor-man's daughter. Meena's brother, Rajesh, was another victim of duplication of Kundan with Shanker. This romance did not fit in with Sunderdas's plans, and he moved quickly to bring about a serious hitch between the young lovers. Meera was dropped the hint that Kundan had something to do with her now missing brother. Sunderdas' plan succeeded as an immediate rift was apparent.
Sunderdas had been patient for fifteen years, but now could wait no longer. With his hireling firmly entrenched both in Dwarkadas's residence, and in the hearts of Kundan's parents. Sunderdas demanded immediate action. The happy-go-lucky lad of yesterday was all of a sudden a tortured soul. The boy who had never even known what the word 'Mother' meant, had now enjoyed all the affection that any mother could ever bestow. Yet he was but an imposter-a low, mean, cheat!
Sunderdas finally fixed the time. On the night of the crime, Kundan tossed in his bed trying to settle his disturbed state of mind. If he did not carry out Sunderdas's orders, he would be exposed before the old couple ! If he did, he would still lose his new-found yearning for mother-love. Aud what of Meera? She might still accept a poverty-stricken yet honest man for a husband, but surely would shun a cheat. Whatever riches his ill-gotten plans had gained for him.
And on to such a scene walked the real Kundan !!
The placid pace of their laves was all at once electrified as events followed one another fast and furious and the story of "Jaal Saz" moved towards its stupendous climax that can only be enjoyed on the screen.
(From the official press booklet)