My dear sister is going through a terrible time. Her MIL died recently (after dementia and being in a home for 7 yrs), and her DH has gone off the rails. His behaviour has been quite extreme and I don't think it is just grief. He hardly visited his mother over the last 3 or 4 years and always talked about her as if she'd gone already. He is barely talking to my sister and when she asked if they were ok as a couple, he said 'I am, but I don't know about you' and has been dropping strange remarks like 'I've got my spies out - the truth will come out soon'. When she tries to talk to him properly he says she is not to push him or she'll regret it. Now he's planning to talk to her at the weekend, but not in front of the children. I think he's being vile and controlling, and my sister is in bits. What can I say to help her through this?