Wife eloped

Hello sir ,this problem is faced by one of my close friends.he is 36 yrs old and married for 6 yrs.he has a 5 yrs old daughter.he is a pharmacist and his wife has been a house wife(passed inter).this persons wife hasnt been maintaining good relations with him for the last 6 mons.but this was only between them and not known to any of the family members.she started being rude to her in laws for about a month.one day she had a big fight with everyone in the family.the wifes parents were called.they tried explaining her but she shouted at every one, scolded them including parents and said she wants to enjoy life.she wants to marry again and not stay here.there werent any major issues till then between the husband and wife.she went away with her parents to her house.after ten days, she eloped from their with some person(a distant relative) and her daughter.their parents filed a missing complaint in the police station.nothing has been known till now through the police.on contacting their parents,they are not revealing details and now say that they are not interested in their daughter now and dont want to hold any talks..but it is known through some sources that the person with whom she eloped happens to be her ex-boy friend(before marriage) and is also a cousin of hers.her parents didnt approve of their relation and got her married to my friend.this was not known to my friend's family..my friend had an issue of depressive psychosis before marriage.was on medication and has been fine for the last 5-6 yrs.he is now on single maintenance medication.this was not known to the wife's family before thier wedding.other than this ,he is absolutely healthy and has no bad habits.he has been loving husband,father and son.. now my frnd wants to know where his wife and daughter are..he definitely does not want to stay with wife again ,wants divorce but wants custody of his daughter.wife and daughter are still missing as said...but they are with sm relatives known to their family people.how do we go about legally?no help from the police.