There is the small matter of keys

or more than one key. No, I have not lost my keys. I know I might. It is always possible.
I keep my keys on a lanyard around my neck when I am out and about in a general way. The lanyard was given to me by the Whirlwind. It is black and decorated with yellow smiley faces. I rather like it. Other people like it as well.
I keep my tricycle lock key, my house key and several other keys that I am likely to use on that lanyard. One of them is a key to my sister's house. It is there for a very good reason. There is another key to her house in the key collection at our place. There is a very good reason for that as well.
My sister is inclined to lose things like that. It is often a temporary loss. She forgets where she has put the keys.
Yesterday she drove her husband into work. He normally rides a bicycle but 42'C is a little too warm for that sort of exercise, especially if you need to arrive looking fit to attend a meeting and not as if you have just come from a work out at a gym.
My sister's household is one of those with more than one car. On her return to their house my sister realises that she has the "wrong" keys because she has driven the "wrong" car. In other words this set of car keys does not have a house key. She has effectively locked herself out.
That means first a short trip to our house. There is nobody home but she can let herself in here because we have a key stored outside - and not, I hasten to add, under a flowerpot. She cannot find the key here. I suspect that by then she was impatient and irritated and did not look as carefully as she should have.
That meant a trip back into the city to get a key from her husband at work. By then irritation was really showing.
We then had a telephone call, "Where was the key?" My father says that one is on my lanyard.
It should not, she tells us, be there. It should be in the cupboard where she can find it. I am certain there is another one. I have since found it. In the meantime I endure a dressing down because the key is on my lanyard. It is, apparently, extremely thoughtless of me. Perhaps it is. Apparently all I need to do if I need to get into her house when she is out is to 'phone her on her mobile and she will come home. We will ignore the occasion she landed in hospital and needed me to get in urgently.
However it would make more sense to have a house key on both sets of car keys would it not?