In an effort to help Tegan recover from the trauma of their last adventure, The Doctor agrees to take her to Earth for a rest. However, a renegade ship and an old foe have other plans.

This week, Paddy and Tricia follow the TARDIS crew as they encounter a new acquaintance and an old friend whilst trying to figure out the strange temporal issues surrounding the ship. Also, what bearing will the presence of a shadowy figure have on their investigation into the mystery of Mawdryn Undead?