What are the remedies against being falsely implicated in a rape case?

My ex-girlfriend's husband called me today (16-Jul-2022) and accused me of raping her when I was in a relationship with her (2018-2020) by mixing narcotics in her drink. We never did narcotics nor she ever drank alcohol with me. My ex-girlfriend and I on two occasions; in 2019 and 2020 spent a week together in a hotel where we had consensual sexual intercourse. I had continued communication with her as she used to confide in me about the domestic abuse she is facing. After the first call from her husband I did not pick the call and he continuously called me ten to twelve times. Also, initially when our relationship started I asked her of marriage but then in 2018 I made it clear that I won't be able to marry her. She agreed to this proposal of casual sex and we continued the relationship without the 'promise of marriage'. Now under the pressure from her husband and in-laws she may accuse me of rape. They have a very constrained marital relationship and there have been instances where the husband beats her and the police have also been involved. What can I do to get legal protection in this false rape case? Also, can I get a restraining order against them?