Ian locks the door but the culprit could be behind the door, or something, so I'm thinking Peter, rather than Cindy herself, or someone else. I think Peter would be feeling a bit pushed out by now with Lucy getting all the attention with the Craig stuff and attempting to run away, and he actually asked her if running was the only way she could think of of getting attention. Also, I thought there was something in the cuts between the scenes tonight, where Ian went into a room or something, it always seemed to cut to Peter and Jane. I had the feeling she knew something, so maybe he's doing it and she was finding the money for the coffin and things. I'm assuming Peter would have a laptop or something as Lucy has one.