"Sounds like your fridge," our visitor, my Webmaster Jerry, suggested.
No. The noise was "SPROING", like a bedspring letting go. And I thought it came from downstairs, not the fridge up in the kitchen.
So I went down to look. I thought I could smell something funny, but when Jerry came down to confirm, he said he couldn't smell anything so perhaps I was smelling Phantom Smells That Weren't There. But after Jerry left, I tried switching on the heater downstairs.
Nothing. Zip. Zilch. Nada.
We tried the other wall heater, in the office.
We checked the breaker. It had tripped.
At this point I called an electrician, who said he'd be there Monday morning.
Monday morning he turned up. We switched the breaker back on, and then he and I went downstairs to see what would happen when the heater was switched on.
What happened was that it blew up. Literally. A spark shot out of it, I screamed, the electrician switched off the thermostat. And went to work inspecting the wires.
Which turned out to have been burned through, because they had been cobbled together originally with spit and baling wire and electrical tape; the electrician kept muttering dark imprecations as he struggled to get it all untangled. The heater, of course, was dead - burned out completely; we took down the whole thing and turfed it outside pending replacement (this was supposed to happen today, but I got a phone call this morning that the warehouse delivering the new one won't be able to do this until tomorrow morning, so we wait.)
I had the electrician check every other heater in the house, with the cats following him closely and inspecting his every move just in case he tried to reverse the polarity of the... ah, wait a moment... delete the Star Trek commentary...Anyway, the rest of the heaters checked out fine, but that one, the big one downstairs, well, it EXPLODED.
What, is Mercury in retrograde again or something?!?