There are so many possibilities for what could happen:
1. Plan is executed as rhea wanted, but ranbir speaks up in prachi's defense and proves prachi innocent (as none of prachi's usual supporters like abhi will be in party so that leaves only ranbir to defend prachi), hence angering rhea more.
2. Ranbir messes up the plan unintentionally hence rhea's execution of the plan is utterly failed as sanju is unable to take prachi into the room. (this is least likely given this diwali party had been kept just for drama and rhea's plan being completely failed to be executed would have no drama element)
3. Ranbir messes up the plan unintentonally by himself ending up with prachi in compromising condition, so rhea's plan to defame prachi by showing her in compromising condition may happen but not the way she expected and instead of sanju being captured with prachi, it could be ranbir, and ranbir also defends prachi. (This alongside number 1 is the most likely to happen as they bring drama quotient that cv's like).
I'm personally hoping for number three as rhea's plan would be executed but he would not be happy about it and would be angry as it would be ranbir being seen with prachi and not sanju, which would make rhea jealous.
I think number 3 will happen because it will leave room for sanju to impress prachi and prachi won't start hating sanju for taking advantage of her. Watching prachi and sanju interact will bother Ranbir and make him insecure. I think sanju might reveal to prachi what is going on between rhea and ranbir if he feels that pranbir romance blooms. At first prachi might not believe him but she will surely start doubting ranbir. Sanju will not easily back off and will keep on pursuing prachi😆😆😆
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