A familiar tale.
We had rodents in the ceiling of the basement (where #2Son lives), and under our floor. The made so much racket at night that he couldn't sleep, so he moved upstairs to the lounge.
So, I poisoned them.
Then we had bad smells.

Then flies startedsoming out of the light sockets (recessed lights, wooden ceiling) at night: big, fat, lazy blowflies.
Eventually, we got rid of them all, blocked all potential ingress holes, and we're OK again.
Dead rat in the watertank? Sounds like my mum: she was staying at my sister's in the country, and said, "This water tastes funny, like something died in it!"
"Don't be dumb", says Sis.
"I'm sure there is!" (Mum's got very sensitive nose and tastebuds).
Turned out there was a big, bloated possum in the tank.
They had to drain it, climb in and wash the tank out with bleach, and buy another tankerload of water.
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