I'm sorry to hear this and I hope you'll be able to get rid of them soon. I live on the second floor and there are 3 floors in my building. I had some mice many years ago before I had any cats. I just used the poison pellets and they ate them and left and then I made sure to block up any holes that I had under my sinks and cabinets etc. I was warned that if they died inside of my walls that it would smell but I never noticed any smell. Good luck.