The Diary of River Song is an audio play series from Big Finish Productions. Alex Kingston reprises her character River Song from the television series Doctor Who. The series is one of the first to prominently feature elements from the revived era (2005 on) of the show; the character of River Song was introduced in "Silence in the Library" (2008) as a time traveller with a mysterious connection to the Tenth Doctor, who does not recognize her. The Rulers of the Universe, the fourth episode of Series 1, sees River crossing paths with the Eighth Doctor, a still younger incarnation. River would appear, again, alongside The Eighth Doctor starting with Doom Coalition 2 and concluding in Doom Coalition 4.