So what could possibly have gone wrong? It was the same sock, one of six, bought probably on the same day and from the same shop as the rest of them, but this one, no, just this one insisted on slipping down her ankle. It’s very annoying walking with a slipping sock, bulging inside your shoe around the bridge of your foot like a deflated lifesaver. Same shoes, same foot, fresh out of the washing machine, it’s still slipping. She keeps stopping to pull it up. So inconvenient in the rain. It may be the elastic band at the top. It’s probably come loose. Though, interestingly, it hasn’t on the other one. Nor does it look loose, no threads hanging. Perhaps it’s her foot? Perhaps her right foot is somehow wrong, unfit for this sock anyway. There’s only one way to find out. She must vary the experimental conditions and try the sock on the left foot. She gets home. Puts the milk in the fridge. Sits down on the bed and takes off her shoe. Pulls up the sock, puts on her shoe again. There, that should fix it.