Seeking help regarding child custody

Hi, would like to request your suggestion regarding the harassment of my mom-in-law towards my child. We are family of four with 4years girl child, whom my mom-in- law abuses and provokes my husband to punish her for very silly reasons. As I'm wrkng and my child is at home alone with her, mom-in-law used to emotionally harass her.I have obsrvd and tried to peacefully resolve the issue, but there is no control and my child used to show signs of depression, even at school, which lead to leave my home and stay at my mother's place.Now my husband is threatening to take away my kid, kindly help me