<human>: Can you provide a brief overview of the text?

My wife and I recently bought a new house (about 6 months ago), and during the holiday season we'd have family gatherings at our new house. 

I never suspected a thing until a few weeks ago my wife finally told me that some of her panties/thongs were missing and she feels like it wasn't just her misplacing things.

Now at the time I just dismissed it and didn't really pursue the problem, but just two days ago, we had a family gathering and I had been noticing throughout the entire night that my cousin was always snooping around upstairs, I've never realized until then that he'd always use the bathroom upstairs for some odd reason every time he came over. 

Our laundry is in the upstairs bathroom and it would be very easy for him to access my wife's laundry basket. I confronted him that night and asked him how come he only uses the bathroom upstairs, he said he has digestive problems (which is true, and why I didn't really care before that he would use the bathroom a lot) and can only go with the bathroom upstairs since hes more comfortable with it. 

I couldn't really say anything to that but it was very very suspicious. At the end of the night after everybody had left, I asked my wife to check if she's missing any undergarments and what do you know, one of her thongs which she had put in the laundry basket is missing.

I don't actually have any evidence of this so I am not certain how to deal with it, I kind of understand that he is a teenage boy but stealing is unacceptable. What should I do about this?
<bot>: my cousin always uses the bathroom upstairs where all the laundry are, made me suspicious that is the reason why my wife's panties keeps disappearing