Then we got the new kitty. We moved the cat boxes back to the spare room. After having them there for a few days we moved them back downstairs. There was an "accident" done on purpose in the spare room. Yesterday we put the box in the basement again. Another "accident" in our room. Kalli thought it was new location and started to relieve herself. I quickly changed her mind. The cats were band from all rooms upstairs. This morning another accident in the dining room. The box came back up from the basement and is sitting at the top of the stairs. We have to find a location that suits us both. The basement is apparently not an option if we don't want to be cleaning up messes. It's current location is not acceptable for us humans, though not two minutes after relocating it there, Patches used it and Kalli went investigating.
I have not found any new messes.