Why is my 18 month old granddaughter afraid of her own shadow? Is it possible she is being abused?

My son and his wife moved in to my home about 6 months ago. This was the first time I met his wife and she seemed nice. The first thing I noticed was that my son can do NOTHING without her being right there, even using the restroom! She was arrested for domestic violence against my son and was required to take a cl which she has completed. She physically abuses her dog and cat if they misbehave and I see my son joining in on the behavior. He was not raised this way. They are staying in a very small room and I know this can be stressful but they are about to move in to a place of their own. My son is working 2 jobs to support his family and leaves his wife and child at home. I hear my granddaughter crying often and if I offer to help she tells me she is being punished for something or other and has to stay in her playpen for a ridiculous amount of time like 4 HOURS! As if that room itself isn't small enough! My daughter-in-law never comes out of the room except to use the restroom, get something to eat and occasionally shower. The only time she lets me see my granddaughter is when I offer to bathe her. That too has been a challenge since she was terrified of the bath when they first moved here. My son would take her in the shower with THEM. He does all the laundry, housecleaning, pay bills, etc. What in the world was he thinking when he married this girl? I am trying to mind my own business but I can't take it any more and I am afraid of what will happen once they move and my granddaughter is all alone with her mother. I want to talk to my son but his wife sees to it that he is NEVER alone. She has control of the cellphone. And to make things worse my son doesn't see any of it. How do I approach the situation with my son without angering him? I am very concerned for my granddaughter and I am afraid they won't let me see her.