Have you ever felt like you were being followed? 

Maybe it was footsteps slapping against pavement behind you that tipped you off or the brisk whooshing of material brushing against itself with each stride. Maybe it was a glimpse of a figure in your peripheral vision—a shadow—something you couldn’t quite make out, but you could tell it was something. Someone. Maybe a whiff of cologne or body odor caught your attention in the breeze or surrounded you in a closed-in space, inescapable.

Or maybe, if ...