Everything in a film is done for a reason SPOILER

When she left her house after the (last, but we didn't know it at the time) rape, she was shown locking her front door. At the time I wondered out loud why she did that, because surely she risked waking her husband up and not making her getaway.

And then fast forward a bit and it becomes obvious why she did it.

Sometimes in good movies, I marvel at the attention to the smallest level of detail.