The Doctor successfully manages to bring Tegan to Heathrow, albeit 300 years too early. However, she may be witness to one of the most cataclysmic events in Earth's history.

This week, Paddy and Tricia follow the The Doctor and his companions as they attempt to survive the paranoia caused by a plague whilst uncovering the mystery of an unexpected comet. Will they be able to avoid the dark fate brought to Earth in The Visitation?