Showing The Bad Place by Dean Koontz

When a distraught and desperate Frank begs husband-and-wife detective team, Bobby and Julie Dakota, to get the bottom of his mysterious, amnesiac 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...