Parts: 1 (45-minute)
Writer: Russell T Davies
Airdate: 21 June 2008
Production Code: n/a

Doctor: tenth
Companion: Donna, Rose

Story: As the Doctor explores an outdoor Chinese market on the planet of Shan Shen, with its exotic fruits and unusual beverages and hawkers selling all manner of goods in their stalls, Donna finds a rather more unusual booth: a fortune-teller, who insists on bringing her inside for a reading and telling her future. Once Donna is seated, the fortune teller examines her palms, and informs Donna that she needs to know more about her past before she can predict the future. For example: how did she come to meet the Doctor? Was there a decision that led Donna down that path? What was the exact moment when she made that decision...?

As Donna ponders these questions, something crawls onto her back. Terrified, Donna tries to leave, but she can feel the thing manipulating her past and persuading her to change her decision. And once that change has been made, Donna in the past moves on to a life where she never knew the Doctor... and, more crucially, a life where the Doctor never knew her. One tiny decision that has ripples which will affect the entire world...