Ongoing sinus bug meant I didn't have much of a sense of smell when I first got up to my mother's, but I kept noticing a faint smell in one corner of the kitchen. Not strongly unpleasant, but not pleasant, yet also not a food (or even off-food) smell or anything otherwise kitchen-y, more gunpowder-y, if anything. I couldn't work it out and was thinking of asking my sister if she could smell anything next time she was a) in the house and b) I remembered (my mother says her sense of smell is pretty useless nowadays).
Then one night as I was getting my supper, the kettle, which sits in that corner, didn't boil after I'd pressed the switch. It's one of those ones that sit on a powered base and can be a bit finicky about precise position, so I checked that, and nothing*. Then I checked the plug, which wobbled under my hand, and plugs aren't meant to wobble. So I pulled it out of the socket, and eek, the back looked like Dali had designed it during his melted clock phase. Which pretty much pinned down the gunpowder-y smell as slowly combusting plug and socket given there was visible singing on the socket as well. As the fuse hadn't blown I had to tell my mother neither the socket, nor the kettle, were safely usable (fortunately my sister had a spare kettle), and that she needs to get the kitchen electrics looked at.
So thank goodness for my sense of smell, however dodgy it may be.
* I'm fairly certain that was the actual problem, but glad I didn't stop there.