The title of this episode refers to a huge futuristic computer named Plato. When the computer is sabotaged and one of its creators is murdered, Cathy is dispatched to the scene to investigate. Wondering why she's been given a solo assignment, Cathy is unaware that Steed is monitoring her every move. But will he be able to save her from meeting the same fate as the unfortunate computer scientist? First broadcast in England on December 15, 1962, "The Big Thinker" was written by Martin Woodhouse; by the timed it aired in America on February 11, 1961, the episode's notion of "advanced" computer technology was amusingly quaint. ~ Hal Erickson, Rovi