Raja Ki Aayegi Baarat - the strange story

Raja Ki Baarat is a serial that appears on Star Plus at 8 PM weekdays (Mon to Thur). It is a show about a girl called Rani, only 17 years old. She is the support of her family after the passing away of her father, and works in the big mansion (who lives in this kind of lifestyle anymore). She is very good at what she does (and she essentially works as a servant in the house), in addition she is very dedicated and honest (although the senior Bhanumathi can't stand her). The other main character of the serial is the prince, Yudhistir, who is very aware of his status. He is not arrogant, but very much aware of his tradition and duties, and will act in the manner prescribed by tradition.
In this family, the Raja Surya Singh Rathore is the strongman of the family, the absolute patriarch; his word is law in the family and he believes in his elder son. In addition, there are the 2 sisters to whom he is married - the Badi Rani and the Choti Rani. The Badi Rani is bed ridden, and does not speak. The entire family cares for her; however, it turns out that the Choti Rani (her younger sister) wants to get rid of the Badi Rani and get the focus onto her son Ranbir rather than the elder son (Yudhistir), who is after all the son of the elder Rani.
Towards this end, she is trying to poison the Badi Rani (her own sister) and Rani is getting caught up in this game, since part of her duties is to attend to the Badi Rani and give her the medicine. Now the Badi Rani is poisoned, her life is saved but she is in a coma, and the blame starts getting put on Rani. How does she get out of this and prove her innocence ?

Here are a whole set of Videos from the serial (link)