An Unexpected Guest (Blue Peter/Doctor Who)

When something about the crew doesn't quite seem right, and a mysterious man in a blue box turns up, what can the three dazed presenters do?
A young girl's mother mysteriously vanishes, and she bumps into them. Can they help her?

A/N: This story got me a Silver Blue Peter badge a few years ago! I am a massive fan of both shows and wanted to do something unique for my badge. Enjoy!