It was notable for providing the first substantial details about Mel's family and general back story in performed Doctor Who. It was also unusual for not having a "villain" per se, and no real alien presence at all. Because of this, and its setting in 2003 and 1782, it was a "pure historical", even at the time of its release. The main "enemy" in the piece is actually the concept of the Grandfather Paradox, and the Doctor's efforts to retrieve Mel from her family's past history without causing damage to Mel's personal timeline.