NC for obvious reasons...
Long story, and I'm reporting this third hand, but seeking advice.
My DBro married a lovely woman who he met while travelling in Central Asia. They have now moved to the UK together. DSIL has no family, and few friends here, so she confides in me a lot.
A few years ago, DSIL had a new colleague from the same country, and they became friends. We'll call the colleague "wife." She then got married and DBro and DSIL became friends with husband too.
A few months ago wife had their first child (and is on maternity leave). A couple of months before the birth, DSIL asked me for advice as wife was being violent and abusive towards husband. This included verbal and emotional abuse, as well as burning him, throwing crockery etc. It wasn't clear whether this was a new thing or not. I suggested husband try to speak to midwife/health visitor for support.
DSIL has spoken to me again and things have escalated. Wife is tracking husband's movements, locking him in the house, isolating him and continuing to be violent. She seems to have blocked DBro and DSIL from contacting either of them, but husband did manage to get a message to DBro that things are not good. Husband said that if she ever did anything to the baby he will leave. DBro's messages back have gone unanswered. Wife won't speak to either of them, or their mutual friends.
I don't know them, or their address, or even full name. DSIL is asking me what she should do. Any advice? TIA