November is one of the most common months for rats to start trying to move in, in our experience, as the cold nights start to really bite. (We've also had squirrels and foxes as guests but that's another story.)
It's a good time of year to double check for rodent entry points all around your...
We get this problem on and off. It's infuriating and you have my sympathies.
First thing to do is to work out where they're getting in because even if you trap/kill this one, others will pick up the trail it's left and will find the same way in. And rats breed very quickly and also spread...