Aasmaan (1984)

When the mother (Mala Sinha) welcomes her son (Rajiv Kapoor) back from war, little does she know that she is welcoming home a look-alike - not her son. But the family pet dog senses something odd about him, and is not fooled. Neither is the sweetheart. But the mother attributes this to the war and will not believe anyone that her son has changed. What will convince the mother that he is not her son? How did the look-alike acquire her son's identity?