Manish-Jyoti were the ghost duo in the other horror flick Vastushastra, which also happens to be the last one I saw. That movie was lot better mainly since the ghost kids were not made to narrate heavy dialogues unlike here.
Plot is simple. Parents go for abortion and the aborted fetus becomes ghost only to haunt them 8-10 years later. 3 years after the abortion, the parents have a daughter. The name of the ghost baby is Gauri and that of the daughter is Shivani. So Gauri keeps watching the happy family and gets upset whenever she sees parents showering their love upon Shivani. So she posses Shivani and then starts troubling the parents. She scares the parents and also tells them that she will kill Shivani after 3 days. Later on, a senti drama follows and she lets them go.
A badly executed horror movie. You would expect a horror flick to grip you and make you wait for what might happen next moment. Nothing like that in this movie. Humans (read parents, their friends and relatives) get to know of the ghost, her agenda and everthing before intermission and after just one creepy sequence. So in a way the movie ended there itself. I mean cummon, the victims are not supposed to know whats going around them in a horror movie. But here, everyone knew everything and they just patiently wait for the ghost to show them magic tricks. Which the ghost does whenever she is in mood. No logic, no reasoning. Once scene she is doing all sorts of nasty things. Next scene she is asking the mom to sing her a lullaby. Total useless junk. The change of heart takes place somewhere during this cat and mouse game. She (the ghost of an unborn baby) gives some big time fundas about how bad a fetus feels about being aborted
. Basically being killed by her own parents when all she was looking for is love. And all this before she was even born. Thank god the baby was aborted. How demanding she would have been 
Lets now come to the acting department. I liked Rituparna Sen in Main, Meri Patni aur Woh but here she was simply bad. Same for Atul Kulkarni. So far, he was good in most of the movies. But then in all of them he had similar roles. Of an ideal journalist, an ideal politician etc. But here in the role of a perfectly normal married man, he fails miserably. Esp. in the romantic scenes. They both looked so uncomfortable doing those scenes. The child artist who played Shivani was irritation at the best. I think it has to do with bad direction. Even the others in smaller roles were as bad. This was some new director Aku Akbar. Infact, this was the very reason I thought this would be a good movie. Since these days most of the debutant directors give very good movies. But this one didn't look even 1/10th as impressive as others.
All in all, avoid it. Just not worth the time and money.