In my mind the following can be the "new enemy" in the order of priority (Rank 1 being the highest), who have sent the letter to Kalavati
Rank 1- Dutta's Aayi
For - 1. She is not Dutta's own mother,
2. She is the most non-suspicious person right now
3. She highlights the point that this is an inside job (The AC Episode) and usually we see in serials that the person who highlights this, is the one. He does this to remove suspicions from him and to mock at others.
Against: 1. To teach the three sisters a lesson, she poisons her own daughter. (Solution - She just wanted to teach a lesson and hence ensured that the poison is in small dose)
Rank 2 - Sups
For - 1. She was the one saved from AC episode
2. She is trying for a way to get out of this marriage. the letter says that to Kalavati that whatever you say is what will happen
3. The letter says that leave Sups alone.
Against - 1.She is shown as timid
Rank 3 - Kishore
I dont want to show any points for and against him as in my mind I am sure he is not the one.
Post your contenders and why do you think so
-DD