This reminds me that if you tell someone not to do something, that's exactly what he will do. It seems that the forbidden fruit is the most desired and I am afraid that our character will fall for it and will open to see what's in the the copper door.
I think the idea of breaking the rules and eating the forbidden fruit is too tempting for most of us as we are thinking of ourselves as better than anyone else. Or maybe that's something that has to do with our survival in a harsh world and configuring our mind to think like that.