Silence in the Library

"Silence in the Library" is the eighth episode of the fourth series of the revived British science fiction television series Doctor Who. It was first broadcast on BBC One on 31 May 2008. It is the first of a two-part story; the second part, "Forest of the Dead", aired on 7 June. The two episodes make up the second two-parter Steven Moffat contributed to the series after "The Empty Child" and "The Doctor Dances" from the first series. It is also the final story that Moffat wrote before replacing Russell T Davies as head writer and showrunner starting from the fifth series in 2010.

In the episode, the archaeologist River Song (Alex Kingston) summons the alien time traveller the Tenth Doctor (David Tennant) to a planet-sized library in the 51st century, where thousands of visitors disappeared without a trace a hundred years earlier when the library was shut off. The episode establishes that River Song has met the Doctor on many occasions but at this point in his life the Doctor does not recognise her.

The Hugo Award-nominated episode is also significant for introducing the character of River Song, who went on to play an important role in future stories.