The BBC has this to say about this years currently untitled Christmas Special.
The special, set during World War II, sees Madge Arwell and her two children, Lily and Cyril, evacuated to a draughty old house in Dorset, where the caretaker is a mysterious young man in bow tie, and a big blue parcel is waiting for them under the tree. They are about to enter a magical new world and learn that a Time Lord never forgets his debts...
DWM issue 439 - Out Now