I think either Sameer has multiple personality disorder ( his mother calling him, reminding of the doctor's appointment gave me that feeling ) for which he's getting treatment , n he has one completely normal sane sweet persona , another blood thirsty killer persona.
I however don't think it's Sameer who'd thrown her off the cliff, because then it'll be kinda too obvious . Rather it may be some one taking advantage of Sameer's mental disorder n plotting to kill Shikha cold bloodedly n place the blame squarely n neatly on Sameer's shoulder. 😳
I can completely identify with Shikha's dad , nowadays what with Delhi gang rape n every day news of horrible incidents happening with women all around the country , the safety of his child is of prime importance to him. I'd have done exactly the same as he did.
The stalker is obviously none other than Sameer himself, but the million dollar question is - why this particular girl ??
As for Manav , he's in all probablity her son , who might be the one closest to her heart.