Maternal Uncle is tortured by aunt

For few months my maternal uncle (mama) is severely being tortured by my maternal aunt and their son (the exact reason is unknown as we were detached with them for several years due to some family reason). They are beating him with rod, slapping him and doing all kind of tortures. But since last few days my uncle (mama) is coming to our and other sisters' house to seek for help. Yesterday he went to one of my aunt's (mother's sister) place, and seeing his bad condition she asked my uncle to stay that night at her place. But at night my maternal aunt (uncle's wife) and their son came to my aunt's (mother's sister) house and forcefully took him back to home. Today again my uncle has come to my aunt's place suddenly and informed that his son and wife beat him with wooden rod, and they have forcefully made him write on a paper that if anything happens to him my mother, aunt (mother's sister) will be responsible. She (maternal aunt) is that kind of a lady who can do anything (I mean "ANYTHING") to get her work done! And I doubt this time also she is planning to do such things to show us as the culprits. Please suggest what to do now.