SPOILER ALERTS!!
I had to watch it twice to get the full jest of the movie. Many of asked (1) Why Ian was killed? The only thing I could come up with was that he was the only one in the family who was not black or biracial. Or, he gave their mother a good life that she didn't deserve. (2) Why didn't anyone call the police? Well, 4 cell phones were sitting in a sinkful of water and it appeared the only house phone was in the kitchen where the older daughter never left. (3) Why was the mother scratching at her wig alot? I think it was her reminder of the fake life she was living.
I wasn't real sure what the delivery guy said to the mother when she said he looked familiar. Did anyone catch that?
I definitely recommend a watch, even a second time to catch the things you may have missed the first time :)