The Unknown (audio story)

 was the first story of the audio anthology, The Diary of River Song: Series Two, produced by Big Finish Productions. It was written by Guy Adams and featured Alex Kingston as River Song, Sylvester McCoy as the Seventh Doctor and introduced Salome Haertel as Rachel Burrows.

Publisher's summary
A planetary anomaly. A scientific impossibility. A mystery to be solved.

Of course, River Song expects to be consulted. She expects her valuable knowledge and experience will help the crew of the Saturnius unlock the strange phenomenon that has appeared in Earth's solar system.

But what River doesn't expect is a stowaway. An infuriating little man, calling himself the Doctor.

Plot
to be added

Cast

 * River Song - Alex Kingston
 * The Doctor - Sylvester McCoy
 * Maddie Bower - Anna Maxwell-Martin
 * Ellen Byrne - Gemma Saunders
 * Robert Murphy - Justin Avoth
 * Computer - Dan Starkey
 * Rachel - Salome Haertel

The Doctor

 * The Doctor stated that he was "overdue a nap", referring to him rarely needing sleep.
 * The Doctor says that one of his best friends is an archaeologist.

River Song

 * Even when her memories are interrupted by the numerous temporal anomalies, the name "the Doctor" rings a bell somehow.

Technology

 * According to the Doctor, he patented the sonic screwdriver.

Plants

 * According to River, during cultivation of Earth plant species on other worlds, the oak tree could never thrive.

Continuity

 * The Doctor recognises that River's device is a sonic screwdriver, (TV: The Husbands of River Song, Silence in the Library et al.) and claims to have invented this technology himself. (AUDIO: The Quantum Possibility Engine; TV: The Doctor Dances, A Christmas Carol)
 * The closer the crew gets to the Doctor's TARDIS, the more the walls of the two ships have combined. One crew member notices "the round things". (TV: The Day of the Doctor)
 * River Song is able to pilot the TARDIS with ease, even when her memory has been interrupted. (TV: Let's Kill Hitler, et al.)
 * The temporal anomalies are made worse by two time vessels colliding in the Time Vortex. One is the Doctor's TARDIS. (TV: Time Crash)
 * The TARDIS has fused with a spaceship before, similarly mixing up their architecture. (TV: Terminus)
 * River Song says that Oak trees are not found on any planet but Earth. (TV: The Android Invasion)
 * The future timeline of Earth has been altered. (TV: The Mysterious Planet, PROSE: The Book of the War, COMIC: Short-Change)