I think it could be the foster son. I don't think they're trying to hide that are they. But of course I'll probably be wrong now!
I did also wonder if he had some sort of special needs.
It seemed to me the bathroom scene was about him having power over his mum, trying belittle her. Either way the episode freaked me out a bit with the son.
I don't think the police officer can have believed her?
It was great seeing Big Mac in it!