In 2006 Dr Adrian Owen and his team made medical history. They discovered a new realm of consciousness, a twilight zone somewhere between life and death. They called this the Grey Zone.

The people who inhabit the Grey Zone are frequently labelled as being irretrievably lost, with no awareness and no sense of self. The shocking truth is that they are often still there, an intact mind trapped deep inside a broken body and brain, hearing everything around them, experiencing emotions, thoughts, pleasure and pain, just like the rest of us. Not quite living, and not quite gone, they have existed silently in these shadowlands. But now, through Dr Owen's pioneering techniques, we can talk to them - and they can talk back.

These shifting boundaries of consciousness have shaken the architecture of our sense of self. We have known for a long time that a body does not define a person - but what if a brain does not define a mind? What does it mean if a mind can exist unharmed within a deeply damaged brain?

Through cutting edge research and case studies that are poignant, tragic and uplifting, Dr Owen maps this inner universe of the self, showing us what it means to be alive and human.