aibu to think that this is sinister behaviour on behalf of mil?

[heartofthesun]

Namechanged.
I like my mil very much but something weird happened a few days ago I can't get my head around. It's seemingly trivial but strange.
Anyway, mil (is 78 and widowed) stopped overnight with us (dc's with my mum).
Anyway, the three of us went out for a meal. Dh let us back in the house with his keys which I distinctly remember him putting on the stairs. There's a lot of keys on the bunch-and a lot of knick-knack type stuff so you can't really miss them.
Mil decided to visit a friend. While she was out, dh had reason to go to car but we could not find keys anywhere, we both thought mil had taken them to let herself back in (fair enough). We listened to hear the key in the lock when she came back. We both think we heard it, but, when asked, mil said the door was on the catch and when asked if she had seen the keys and to think about whether she had seen them she replied that she had not.
Anyway, yesterday she calls to say that the keys were in her handbag (!)
I can't for the life of me see how a (large) bunch of keys found their way in there. Either she is playing a weird trick or losing it. I fear it's the latter as she is not vindictive. Perhaps I am being unreasonable to think this. I just don't know.

yes it is heart - something nasty waiting to emerge. Hopefully not the case

Thank you, StealthPolarBear- I wasn't expecting the English lessons from others posters. It sort of misses the point!
Anyway, in itself it may be nothing, I agree. Just have to watch out for other things. Thanks.

Although I have used the word 'sinister' properly here.

'Course it's a correct use of the word. As in "I have my tenth headache of the day: I do hope it's nothing sinister." I say that sort of thing all the time

Anyway to the point - just a one-off senior moment I reckon. Hope she and you have a nice Christmas!

It's the connotation when applied to behaviour which makes it an odd choice of word in this situation, though. It makes it sound like the MIL's motives are sinister. Although perhaps people are only contextualising it that way because this is Mumsnet

You mean because this is MN and the thread title has "MIL" in it

Exactly!

Neither sinister nor losing it - I reckon this was, in common parlance, a 'senior moment'. I quite often go into a room and then cannot remember why I went in there - and I am in my 30's!! I think you are over-thinking it!!

Sinister

adjective

1. threatening or portending evil, harm, or trouble; ominous: a sinister remark.
2. bad, evil, base, or wicked; fell: his sinister purposes.
3. unfortunate; disastrous; unfavorable: a sinister accident

saying "Sinister behaviour" would make most people think that you wondered if the behaviour had been intentional for a bad reason, not that you were worried if she was losing her marbles... I would expect someone to say "worrying behaviour".

Helpful, Squeaky - so OP had in fact used two of the possible three meanings, viz., 'ominous' (see [1]) and 'unfavourable' (see [2]).

The OP cannot help the poverty of the average MNer's vocabulary

I'd say doolally rather than sinister. Just the sort of thing my mother-in-law would do. I could fill a book with them

She probably had copies made while she was out and is selling them to local thieves.

When I was a medical typist I quite often used to see the word sinister used in letters in a medical context - as a synonym for serious/worrying. Now the OP has clarified, I can believe that's what she meant.

Something happened yesterday that has made me a little bit more concerned: mil turned up at my sil's (i.e. her daughter's) house who lives 100 miles away from her house with no prior warning beforehand. It was not meant as a 'surprise' visit; just that mil -who was not 'just passing' on her way to somewhere else-decided on a whim to visit her daughter 100 miles away without informing her first. This is strange, isn't it?