This happened a couple of days ago. We have a small freestanding battery operated motion detector alarm in the shed to ‘protect’ the bikes. It’s a couple of years old and has only gone off once in that time (wasn’t a burglar, probably a mouse or something).
I noticed it wasn’t working and brought it indoors to replace the dead batteries. Tested it and it worked fine. Didn’t take it back to the shed as it was dark, tipping down and I was being lazy, so left it on the hall table, forgot about it and went up to bed.
About 2am, the alarm goes off. Scares the crap out of me, but I pull up my big girl pants (DH is away, typical) peek over the bannister but there’s no one lurking, so I check the doors, reset it and go back to bed.
Around an hour later, it goes off again! Down I go but this time I turn the detector part to face the wall, so it’s almost touching but not quite. Back to bed.
Wide awake trying to work out what on earth is going on but eventually nod off, only to be woken by the bloody thing screeching yet again.
This time, I remove the batteries and get some undisturbed sleep.
It was probably a very skinny spider running inbetween the detector and the wall, or something technical, I keep telling myself.
It’s back in the shed now and has been silent ever since.