What can I do against dowry harassment?

I am seeking urgent legal advice and guidance on a distressing matter affecting my family. My real sister's husband has subjected us to severe emotional and financial distress. During the marriage, our family provided a dowry amounting to almost two crores INR, which included various assets such as a car, gold, and other valuables. Additionally, he took my brother's motorcycle and my scooter without consent or legal transfer. The situation has worsened recently as my sister has been diagnosed with chronic kidney disease, kidney failure, and is currently battling for her life in the hospital, with the added complication of brain TB. At this critical juncture, her husband has not only neglected her care but also engaged in a heated argument, verbally abusing us in the hospital. He explicitly stated that he refuses to take responsibility for his wife's medical expenses, leaving our family to shoulder the burden alone.