I'd agree very much with hop-daddy that dreams are somewhat tricky to interpret. I have learned dream interpretation from a couple of teachers and even with years of interpretation, there is no guarantee on the accuracy. Yet, here, I will give my insight as to what this may mean, so this is more of an opinion, open for discussion.
Let us start from the most solid part, where the lighting in the dream and the room is the same. This would tend to indicate that the dream is telling about something in the present. The part where you dream about seeing yourself, I very much agree with hop-daddy's interpretation, that you are tapping into something spiritual. The next significant clue we get is that the incident is occurring on your bed, indicating that it is very close to you perhaps even intrapersonal. In feng shui, the bedroom affects personal life and relationships, and the bed is the first thing to consider when arranging a bedroom. Next, when we look at the nightgown you are wearing, there are a few things we can consider here. First that it is a nightgown, meaning something worn when going to sleep / rest. Second that it is not the nightgown you have on, yet one in your possession. Clothes in symbolic dreams usually indicate a role you play, such as mother, friend, associate, employee, consultant, teacher, student, these are all roles. A nightgown would indicate the role that is played between the 'awake' world and the 'dream' world or 'metaphorical' world. This would indicate a role such as a shaman, an intuitive, a seer, even an empath. There should be a 'feel' about the clothing, that can give more precise indications. Finally we have the 'shadow' holding 'you' hostage. This is indicative of the shadow self holding the particular 'role' hostage. The shadow-self is what most people commonly refer to as the ego. Yet, its important to understand the the shadow-self is merely one side of the ego, the ego can be very helpful if it wants to. Now then, this particular shadow self is clad in black and white, which reminds us of the clothing worn by convicts of past eras. More than that it tells us of black and white, the story of shadows and judgement.
Now, putting it all together, we find a message that says that your shadow-self is holding a part of you hostage. That part of you being held hostage is that part that connects your spiritual self to your waking self.