5. The Fourth Doctor's Fateful Decision
From: "Genesis of the Daleks"
Premiere: March 8, 1975
Portraying the Fourth Doctor in only his fourth adventure (and already no stranger to chewing scenery), Tom Baker grapples with the greatest ethical dilemma of his life. Simply by crossing two wires, the Doctor can eliminate the Dalek race in its cradle. Urged to do so by companion Sarah Jane Smith, the Doctor ponders the enormity of the act: "Listen, if someone who knew the future pointed out a child to you and told you that that child would grow up totally evil, to be a ruthless dictator who would destroy millions of lives, could you then kill that child?"