Dearest reader,
I understand that the matter is severe and this needs immediate action for the safety of the wife. Here I am to provide you with some pieces of advice, that might help you out.
Firstly, this is a case of domestic violence and needs immediate legal action for the protection of the victim. You can ask the family of the victim to file a police complaint in the nearest police station under Section 498A of the Indian Penal Code (IPC) as mental and physical cruelty by the husband or by any of his relatives is punishable under the law. Filing a complaint against the husband will get him arrested and start certain legal proceedings against the abusive husband.
The family can move to the magistrate to seek a protection order for their daughter under Section 18 of the Protection of Women from Domestic Violence Act, 2005 (PWDVA) as this provision prevents the husband from threatening or harassing his wife. Additionally, the court may also issue a residence order as per the concept mentioned under Section 19 of the said act, ensuring the safe accommodation of the wife.
As you have mentioned the husband is threatening her wife which involves assaults or acid attacks, then this should be immediately reported to the police under Section 326A of the Indian Penal Code (IPC), this has been made necessary to report these types of crimes. Acid attacks are treated as heinous crimes involving strict penalties, including imprisonment, fine, or both.
Referring to the case of Arnesh Kumar v. State of Bihar (2014), you should encourage the wife and her family to gather the pieces of evidence and file a complaint against the husband as soon as possible for the sake of her safety and protection.