In the conclusion of the two-part story arc "The Edge of Destruction" (aka "Inside the Spaceship"), the TARDIS has been thrown off course and its occupants are hurtled to the beginning of time, or, as the Doctor (William Hartnell) refers to it, Event One. In a surprising display of ill will, the Doctor, Ian (William Russell), Barbara (Jacqueline Hill), and Susan (Carole Ann Ford) take turns blaming one another for the present crisis. But as it turns out, the TARDIS itself is responsible -- and the "danger" at hand may actually be a blessing in disguise. Written by David Whitaker, "The Brink of Disaster" first aired on February 15, 1964. ~ Hal Erickson, Rovi