The Pod Goblins started the evening off by educating us on the different kinds of equipment they use, and the best methods they found for using them. They then shared past experiences with the mill, telling us about noises, shadowy shapes, apparitions and EVP. After that, they let us loose to go on our own adventures.
My wife and I explored all the different buildings and didn't find much until we hit the smaller mill. While we were sitting in that building, we experienced something knocking on the window behind us with three distinct knocks. Granted, the wind was blowing so I was a bit skeptical at first. However, I turned on my voice recorder and asked it to knock again, and it did. I've included the audio below in a YouTube video (the knocking occurs at about second 14). It ended up knocking a few more times after that, always after we asked it and always with three distinct knocks. I figure if it were the wind, then it would be more erratic.