In high school many moons ago I worked at a reasonably large furniture and decorations retail shop.
One day we had a customer who came to the till to say she'd accidentally dropped and broken a decorative item. "Sure, no problem" we said, as the displays at the store were precarious at best and stuff broke all the time. We just wrote it off.
Some time later (we got busy with other customers) I hear a crash and go to investigate. A shopper has broken a piece of pottery. No problem again, I go grab a dustpan from the back and start sweeping. Only after I've cleaned it up do I begin to realise that it's the same lady from (at least half an hour) earlier.
I don't have much time to ponder it as I get busy with other customers again at the till. About an hour later, the phone rings. I pick it up and a woman on the other end frantically asks me if there is someone in my store and describes the [clumsy] shopper I had dealt with earlier. I tell her I'm not sure if she's still in the store but then catch a glimpse of the customer in the distance and confirm to the caller. The voice on the phone then proceeds to tell me that she's the daughter and that her mom is the shopper and that she has narcolepsy. She's not supposed to go out unsupervised and had apparently "snuck out" and driven herself to our store. The daughter tells us she's on her way and hangs up.
Then of course my attention is on the customer who I find and spy on a bit. The woman is moving slowly around the store, browsing. When I see her pick up a plate, as she's holding it her head starts to nod and her hands loosen and I suddenly expect to be writing off my third item of inventory for the day. She manages to catch herself though and moves on and, not knowing what else to do, I move back to the till where again we are busy.
Eventually this lady shows up at the till with two or three small items (she's been in the store about 2 hours by that point). While I'm checking her out, she nods off again. More than once. The whole process takes ages. Eventually she's served and then as she walks out of the store, I realise she's walking to the car and I panic realising she shouldn't be driving. I watch her through the windows as I do a return dial trying to get a hold of her daughter with no answer.
I'm afraid to let my eyes off the lady as she stands for what seems like an eternity at the driver's door of her car. Seemingly looking for her keys and at one point dropping them. My boss is in the back and my coworker is swamped with other customers. I call the back room and am desperately trying to explain this bizarre situation while at the same time panicking that this lady is about to get into a car, in no state to drive and, as a shy high schooler, I had no idea how to (politely) stop her. Just at that point the daughter shows up and confronts the mother. I see it all through the shop window and I start finally breathing again.
The daughter comes into the store to apologise. I felt so bad for her having to worry after her mother all the time, but I also of course felt most sorry for her mother who seemed like a sweet lady but obviously was being driven nuts and felt she had to try and escape from this awful disorder ... by coming to our store!