Dad: (since he has taken the antidote) He lies to Ritu so that she thinks that he is a murdurer and then she can make some other plan. this revelation has confused her and now the new plan she makes will go completely hay-wire and she will do something wrong.
mom: (since he has taken the antidote) he has lied to Ritu so that she thinks that he has killed naveen. she will tell this to naina. Raj actually wants to test how much Naina trusts him and so he knows that our vamp, ritu will surely tell naina. Remember that when naina asked him if he trusts her he said that we are all humans and we all make mistakes. he tested Aalekh and Huda by sending the Alcohol. now he will test naina with this.
Me: RAJ KILLED NAVEEN! I think he did it by mistake or as a mercy killing for naveen. I always knew that something was fishy. when he was telling naina of naveens killing he said that naveen shot himself. But whenever they would show the flashback the would show that some1 screams "gaddaar" and then sum1 shoots naveen. naveen has no gun and looks completely shocked when he realises that he has been shot.
Now i hope that stupid naina does not suspect him wrongly (she is capable of that. remember those fake letters written by ali on bhargavs orders? she suspected him)
GOD SAVE RAJ AND THE RN JODI!