Daag is the story of a man wrongly convicted of murder, on the run from the law. Sunil ( Rajesh Khanna ) is forced to leave behind his new bride Sonia ( Sharmila Tagore ), when he kills her would be rapist.
In an attempt to establish a new identity Sunil meets Chandni ( Rakhee ) and ends up marrying her to give her illegitimate child a fathers name.