Set in Mumbai, Kasam is a story about Rishi and Tanushree who fall deeply in love through a twist of fate and the vagaries of destiny. But life has something all together different planned out for the two.
Rishi who has some dosh in his birth chart can only get rid of it, if a girl with the opposite planets in her charts marries him. Tanushree and Rishi meet each other when Tanushree saves him in a near death accident and Rishi ends up falling in love with her. On finding out that Rishi has some issue in his kundli, Tanushree decides to sacrifice herself for him and marries him. The moment after their marriage, Tanushree ends up dying in a horrific car accident. Rishi who is very deeply in love with her doesn't take it too well and decidess to break all relations with Gitanshu Gupta who was driving the car which took her life.
Later, he gets to know from his mother that Tanu got married to him knowing fully well how her life would be at risk if she gets married to him. Shocked he checks her kundli and comes to know that his mother was right â€“ Tanu did know and took his death on her fate... and that makes it worse for him...
He goes off to confront the tantric who predicts that in their case love will be more powerful than any saaya...and shadow of death... and that Tanu will come back to him by the next puranmashi ki raat.
And she does â€“ but in the most unexpected form... for she is reborn...and she comes into his life 20 years later â€“ in the most unexpected twist of events and in the form he expects the least. Face is different but the attitude is just the same. Her outwardly appearance has completely changed but the rest of her- her mannerisms, her behavioral patterns, her idiosyncrasies, and her soul is just the same.
Kasam is that ultimate story of reincarnation â€“ of love in its purest, unexpected and most powerful forms.