1968: Cristian Alvarez meets the Doctor in London.
1978: The great temple of the Aztecs is discovered in Mexico.
1980: John Lennon is murdered in New York.
1994: A gunman runs amok in Mexico City.
Each time, Cristian is there. Each time, he experiences the Blue, a traumatic psychic shock. Only the Doctor can help him — but the Doctor has problems of his own. Following the events of Blood Heat and The Dimension Riders, the Doctor knows that someone or something has been tinkering with time....