Once a month my wife's aunt and her daughter come to our beach house for the weekend. My wife wanted our bedroom to be on the loft where we have a private bath. We had a contracter com in and it is beautiful. The toilet and sink area has only a curved wall around it and the shower is huge with five jets on the wall and surrounded in glass. My wife and I shower together often and I also like watching her shower and she watches me alone somtimes. Its like a suite in a fancy hotel and we both love the way it was finshed. What we never thought about is that the ouside deck is accessable from the second floor guest room where her aunts daughter Sara sleeps when they are here. We always close drapes over the sliding door but a few feet away is an octagon window with no coving in it. One afternoon as I got out of the shower I went to my dresser and through the mirror saw Sara stairing in at me from the bottom of the octagon.. My wife and I had just showered together and we had masturbated each other. My wife was inside the toilet area at the time and when she came out Sara dissapeared. I was going to tell my wife about it but decided not to knowing how it would upset her. Sunday afternoon I came back from the beach early and my wife and her aunt went to get take out seafood. I didn't know where Sara was and went up to the loft to shower and change out of my swim suit.. There she was again at the octagon window watching me shower. I know I shoud have put a stop to it right then but It aroused me knowing she was watching me. I showered dried off and got dressed knowing she could see me and I never told my wife or aunt about it. Sara is 13 and a fat little spoiled brat, but for some reason it turned me on knowing she was watching me. That was last July and everytime they have come since then Sara goes up the ouside stairs onto the loft deck to look in that window. She has seen me naked every one of those weekends since then. I don't feel bad about her seeing me like that but she has also watched my wife and I shower together many times. My wife would die if she knew about it. When we do shower together we have had intercouse at times but mostly just wash and masturbate each other. If I am alone and Sara is at the window I have also maturbated most times letting her see me doing it. When she does talk to me she is very good at hiding the fact the she peeks in the window at us. I don't know if she is looking in when my wife is alone in the loft and acts innocent the few times I have mention the deck. I puposely once asked her if she has ever been on the top of the decking and she denied ever being up there. When she looks in the octagon window she is only a few feet away from the backside of the shower enclosure. The glass is made up of a mixture of smoked glass, riddeged glass and and clear glass on the sides and bottom where she looks inside from. She has to bend a little to look in because the rest of the glass is not transparent. I know I should tell my wife and Sara's mother about it but it excites me both when I am alone and also when my wife is with me. Sara is so polite and friendly with everyone, nobody would ever suspect she is such a sneak. I'm the only one who knows what and how she is doing this.