It was a mystery surrounded by a riddle wrapped in an enigma.
It came in the middle of last Sunday night, when all right-thinking Bathonians should long since have trundled up the Wooden Hill to Blanket Fair.
It was weird, it was loud, it was eerie. And the following morning, on thisisbath.co.uk, the mystery got its first public airing:
"Bath baffled by big bangs" read the headline, and by golly were we baffled.
Not a few West Country towns and cities are known for their strange noises. Gallons of ink, for example, have been spilled dissecting the mystery of the so-called Bristol Hum.
Others are not so well known: you can Google for hours without finding any mention of the Gloucester Rumble or the Shepton Mallet Whine.
And yet, and yet...
Bath, blessed in so many other ways, never had its own special noise. Until Sunday, that is, when it got The Bang.
Early reports of it came through on Twitter, as they always seem to these days. One bang was heard at 11:43pm, the other about six minutes later.
And that was it. Everything went quiet again. Except for Twitter.
Now the really strange thing about all this auditory upheaval was that Dixon Junior and yours truly heard the bangs almost exactly an hour earlier. We were watching Match of the Day, and we thought it was Mrs D thumping on the bedroom floor for us to turn the telly down. And we did, sharpish. But the following morning she denied all knowledge.
So what was it that we heard? A pre-echo of the sound reported on Twitter an hour later, transmitted through a wormhole in the space-time continuum? (There's a lot of those up our road. Not as many as there are potholes, though.)
Were they sonic booms, or fireworks, or even, as some wag suggested on thisisbath, property prices going through the roof?
Perhaps we shall never know. Shakespeare had a point, though, when he wrote in The Tempest:
"Be not afeard. The isle is full of noises,/Sounds, and sweet airs that give delight and hurt not."
Perhaps he'd heard the Bath Bang.