I studied the grid a little closer and realised that she shouldn’t have placed the “4” there. There was already a “4” in the bottom of the column and based on the answers she’d filled in so far, she should have in fact placed either a “1” or a “3” in the box. I had a huge compulsion to point out her mistake but then that opens a whole jockstrap full of crabs as it would reveal that I’d been spying at her puzzle over her shoulder.
What is the etiquette in situations like this? Should I point out the failings of a stranger or leave the status quo knowing full well that placing the “4” in the wrong place has thrown every other placement out of whack in a move similar to a butterfly beating it’s wings in China. At this point her mobile rang with a horrible polyphonic explosion of Kung Fu Fighting. I relaxed and let my staid, non-confrontational side win. If she thinks its amusing to inflict faux-Asian 70’s pop on the rest of us then fruitless repetition followed seething rage as she realises her mistake is far, far less than she deserves.