If the shriek was from an animal, even unseen, this would most likely be the call of your anima (the feminine/primitive/instinctual self). My first reaction here is to wonder what owls represent to you, barring the predator/being hunted situation. What an animal represents in the dreamer's mind will often relate to what their presence in the dream is related to...

You talk about the whiteness as if it's not an emptiness, but something more like a veil. Something that is keeping you from seeing/interacting with the world... I see that you have agoraphobia on your concerns list (yes, I check that - you'd be surprised just how much that list helps with interpreting dreams ). Has the phobia been worse lately? Is it creating a cause of concern? This would be the most likely source of something removing you from the world.

Waking down the isolated path would simply be the reflection of feeling lost and not knowing where you're going or what you need to be doing (you practically said it yourself). So then ask yourself, where in your life are you feeling directionless/without purpose? That may be what the majority of this dream relates to. Then consider the following two thought points...

--> How is your phobia making this situation worse?
--> How do traits that relate to your meaning of what an owl is give you strength?