Strangers by Dean Koontz (1986) Putnam

A priest has a crisis of faith.  A writer starts having nightmares.  An ex-marine cannot stand the dark.  A surgeon starts having fugues and running away.  A thief gets a sudden need to give the money he's stolen away.  What do all these strangers have in common?  And who is sending them clues about a motel they stayed at two summers ago?