I see the separation that you are trying to convey. I can even understand the use of shadow. I still just don't get a feeling of separation. Perhaps if there had been a person in prison uniform looking towards the top of the wall you would have hooked me. But as is I just am not able to find the story you are trying to tell.
Wow, that's a nice blue sky, and it's VERY different from the dark wall. A touch of fill flash would have bumped this up about 2 points for me, I think. I like the theme! 7