The bad place - Dean Koontz

Frank Pollard awakens in an alley, knowing nothing but his name - and that he is in great danger. Over the next few days he develops a fear of sleep because when he wakes he finds blood on his hands and bizarre and terrifying objects in his pockets. 

When a distraught and desperate Frank begs husband-and-wife detective team, Bobby and Julie Dakota, to get to the bottom of his mysterious amnesiae fugues, it seems a simple job. But they are drawn into ever darkening realms where they encounter the nightmare, hate-filled figure stalking Frank. And their lives are threatened, as is that of Julie's gentle, Down's syndrome brother, Thomas. 

To Thomas, death is the "bad place" from which there is no return. But as each of them ultimately learns, there are equally bad places in the world of the living, places so steeped in evil that, in contrast, death seems almost to be a relief...