Doctor Who - Catch-1782

When the Doctor and Mel visit the National Foundation for Scientific Research as it celebrates its centenary, Mel expects only to be able to catch up with her uncle. She doesn't expect to meet her own ancestors... What is buried in the grounds of the Foundation? What secret has Henry Hallam kept from his descendants for three hundred years? Can Mel escape her own past? Visiting your relatives can sometimes be trying, but surely it should never be this difficult?