How'd he get in

A rat is running around in my walls, I could hear his footsteps quick but heavy leaving a trial of misfortune and commotion, how did he end up in there I ask myself Who let him into my walls Is there a hole I do not know about? He gives away his spot and runs down to next open space he can get to before I find him, Leave I tell him and he does not understand Well of course he doesn't, he's a rat I try to reel him out with some cheese and nuts Although those do not satisfy him as much as my thoughts, Please go Mr. Rat I have suffered enough, your running is causing me a headache, My walls are weak and thin Maybe that's why you have ventured in It was an easy spot to lay and you stayed