scary eyes looking back at me

I was about 11 at a friend's party in their garden and I looked through a crack in their shed. I saw a pair of eyes staring right back at me. To my memory it was complete darkness other than the eyes and they were definitely not my own. I got the feeling even then that they were the eyes of an adult. No one believed me never mind had a look inside the shed. It really doesn't feel like it could have been a mirror. The eyes looked so different.

I'm wondering what people's thoughts are on here?