Husband harassing wife

We are all from a very well educated family and we have very good respect in the society. We have always been good to people around us. My sister got married in Feb 2014. As it happens in some of the indian marriages, the boy's family cribbed that they didnt get "good respect" from us .. While we still paid them lot of money during marriage as and when they asked to uphold the marriage, the boy's family packed their bags and were about to leave without my sister... We were all shocked and when we questioned and cried and begged them, they boy's family agreed to take my sister.. That was the beginning.. we have been keeping all that aside to have optimistic view and then, her husband and her father-in-law and mother-in-law immediately started harassing her to transfer all the money into her father-in-laws account. They have been asking her to do all sorts of things and my sister kept on doing them just to gain their trust and to avoid any conflicts with them.. Then 2 months down after marriage... her mother-in-law have said the most inhuman things (which i cant tell here publicly) to my sister to torture her mentally and physically and then her husband pushed her outside the house.. My sister was in a shock that time and was into depression… she stayed with me for 2 weeks and her husband apologised for what her parents have done and took her back with the condition that his parents wont interfere again and he wouldn’t torture her.. Things were fine later and we thought that they have settled.. Again 2 months later, he asked her not to come to the house.. when my sister still went to their house, he dragged her out of the house, pushed her head against wall and hit her.. my sister again came back and its been more than 1.5 month now.. he stopped responding to calls and he is not reachable also .. My parents are very kind hearted and they don’t want to initiate any police complaint and are still hoping he will come back .. but I think that we should file a complaint and make him a lesson learnt the hard way.. my sister is confused on what to do now.. and all of us are in severe mental pressure.. We strongly suspect that the boy’s family wants to get him marry again to someother girl … and hence, they are trying all this on my sister to push her and make her ask for divorce so that he can marry again and make more money.. I want to free my sister from such money-minded and cruel people.. but want to make him face punishment such that he will have tough time ahead.. it should not be like a boy marrys a girl just to get money, spend time with a woman and then try to harrass her to get rid of her and then marry another woman.... I want to stop that… What can we do now? Pls advice how should we proceed..