The vault that keeps opening onto itself

Last night I dreamt I was back at the old job, drilling a safe that turned out to have no back — just another dial behind the plate, then another, each one perfectly oiled and quiet. I kept spinning tumblers and hearing that soft click that means almost, and I woke up with my fingers twitching like I still had a feeler pick in them. Never opened the last one. Probably for the best.