Written by Steven Moffat (Previous Episodes: “The Empty Child,” “The Doctor Dances,” “The Girl in the Fireplace,” “Blink,” “Silence in the Library,” “Forest of the Dead,” “The Eleventh Hour,” “The Beast Below,” “The Time of Angels,” “Flesh and Stone,” “The Pandorica Opens,” “The Big Bang,” “A Christmas Carol,” “The Impossible Astronaut,” “Day of the Moon,”…