Nail biter. Jaw dropping. Gripping. Any and all of these words don’t come close to describing what transpires in “The Third Rail.” If you are at all claustrophobic, take note; this will probably be a tough episode to watch. Nearly every scene is wrought with tension, amplifying your anxiety and nervousness for what will happen next. From Gus (Miguel Gómez) making a horrifying discovery when he gets home, to young Zach (Ben Hyland) leaving the sanctuary of Abraham’s (David Bradley) pawn shop on a fool’s errand, “The Third Rail” will have you glued to your seat— although you’ll probably be watching through your fingers most of the time.