Wispy Ghost Picture

"We were taking pictures of my grandson looking for Santa, when in one picture there is a circular thing next to him. In the next photo was a slight wispy thing. Last night we were looking at the pictures, so I told my daughter to go upstairs and just take a few random pictures looking at the same window. First shot she got nothing; second shot she got another wispy thing; third shot she got (this) big wispy thing. It is not smoke. Pictures were taken about 10 PM and the window in the picture was open. We tried again about an hour later with the same set-up and nothing was captured."