So I just watched the video of today's episode on zippyvideos.com if any of you are interested, cos the current link is not working too well. Anyway i reckon the person behind the door, can be of 3 people:
1/ guruji which everyone has guessed
2/ shashank (highly unlikely, but possible)
and finally,
3/ a family member who is estranged from the Kapoor household, and only Nikhila probably knows about this!! LOL.
Also did u see when shiv and nikhila were talking about the raaz in the bedroom after her pill taking possible suicide case, nikhila kept saying how they both know its about happiness for both people, i wonder what she meant? Maybe i misunderstood the plot!!
Anyway let us know if different observations are seen!!
Enjoy!