To me it looks that the investigation is not going on the right path. I think the police has now got the doubts on her mother which they might have got it well before. Ok if we take it for granted that her mother or father killed her but who killed Hemraj.To the extent a woman can go to take revenge no man can get near to her thoughts as they are very intelligent. Iam not saying this - the police records of india or might be of any other country you can find one common thing. The crime done by women is more perfect than a crime done by male.Cant the mother be he mail culprit. Arushi's mother might have had some illicit relationship with hemraj and he might have been seeking or black mailing her and in the mean time Arushi might have come to know about it.So arushi's mother wanted to get rid of Hemraj so she killed him firstand in fear of leaking this out she might have killed arushi too.If a man had committed the crime then he would have carried the body of hemraj by lifting but not by dragging. And Dr.Talwar is a fit man.
