Domestic Violence/mental torture and threats of murder

Dear Sirs, we are residents of Kolkata West Bengal, my sister got married 2.5 years back in Pune...she was their till June last year when she was expecting (she delivered a baby boy in August 2015) to escape mental torture during pregnancy...also though not explicitly they made demands of a flat and a car..she got him a moped as well.. everything was going fine until they found out that she delivered a baby boy...first he tried to persuade her claiming that he got himself diagnosed for hyper-aggression and that now they can live happily ever after when she refused to go he threatened to take her child away (who is one month to 1 year now)...she has switched off her phone so now he has started harassing my father daily over phone ... She is afraid to take any action lest he will take away her baby...we are afraid too...please advise to what possible actions can be taken and who other than my sister herself has the locus standi...also please advise if she can file a complaint here in Kolkata (if she plans to) or will have to do that in Pune only awaiting your reply. thanks in anticipation