Video: Is this a ghost or just an elderly woman?

Do you believe in ghosts? If you don’t, then maybe you should watch the following video first.

As reported in the Daily Mail, 88 year-old British pensioner Dick Williams recently noticed evidence of badgers and animals in his garden outside his house, and decided to set up a night vision camera outside his home to capture the animals.

http://www.youtube.com/watch?v=pdSZkfgIVOs&feature=player_embedded

When he looked at the recording the next day, he was shocked: it was a video of an elderly woman walking in a nightgown through his garden. Unfortunately, the video only shows the back of her legs, and no face.

Williams told the newspaper that there is an assisted living community near his house, and he initially suspected it was a resident who had accidentally wondered off, but he contacted the police and there was no record of anybody missing.

“I don't think it's a ghost. I don't believe in them - but of course people can make up their own minds,” he said.

Williams lives in Shropshire, England, near the Welsh border, with his wife Nora, but says it was neither him nor her in the video.
What do you think? Is this a video of a ghost, a hoax or just an unexplained happening?