Me, Abbie and an Unknown Culprit!

I am back at Abbie's and she loved seeing me. She always wags her tail and lets me know that I am a welcome member to her household. However, I didn't realize the household had grown. Abbie lives in one of the nicest homes I stay in. Always organized, immaculate and very well appointed inside and out.
We decided to settle in and watch some television tonight. We typically stay in the master bedroom as Abbie is used to sleeping in this room. We were busy putting some last minute things away when both of us heard something. No kidding, she perked her head up at the same time I perked my head up. We listened intently for a moment and then looked at each other as if to say 'What was that?'
Now all kind of things are racing through my mind. We followed the noise. It was a rustling noise as if someone or something was going through clothing. We approached the bathroom and soon discovered the noise was coming from the closet in the Master bathroom. We both stood by the door listening and what noise had once stopped, it was now beginning to get louder. My heart was racing and I kept thinking whatever was in there was big enough to make all this noise. Naturally, my first thought was that there was a person hiding in the closet. Of course, I wasn't being very logical at this point as nerves had taken over. Abbie and I went to the kitchen and got a knife and then I promptly went back to the closet door and said 'Whoever is in there better come out because I have a knife'. Yeah, right! I pride myself with having a good sense about me, but in retrospect, this was probably the dumbest move I've made to date!
When I realized a person could not have gotten into the house without breaking a door or setting off the alarm, I decided I was safe, but kept the knife anyway. We continued to listen to this relentless noise. It was not frightened by our presence. It was large enough to make rustling noise through the clothes in that closet. AND....we could hear it knawing on the inside of the wall.
We left the bathroom after spending a LOT of time talking to whatever is in there. We left, closed the door and refuse to use that bathroom at all!
I don't want to alarm Abbie's Mom and Dad, but I thought you should know that your family has grown! Stay tuned for an update on our friend!