The Boundless Sea (audio story)

 was the first full cast audio story in the first series of The Diary of River Song, released in 2015 by Big Finish Productions.

Publisher's summary
River Song has had more than enough excitement for a while. Deciding the universe — and her husband — can look after themselves, she has immersed herself in early 20th century academia, absorbed in writing archaeological theses.

But when a mysterious tomb is found in a dry, distant land, excitement comes looking for River.

Can Professor Song stop any more members of the expedition from dying? What deadly secrets lie buried within the crypt? And will British Consul Bertie Potts prove to be a help, or a hindrance?

Plot
The queen of an ancient tribe is being buried alive with her late husband. She protests, but the priest leading the ceremony seals the tomb with her inside. Such is the tradition.

In Great Britain, Professor Straiton, an archaeologist, receives a call about a discovery of a 3000-year-old tomb in Lower Mesopotamia. They discuss whom to send there and decide to ask Professor Song, a visiting professor. However, River Song has no intention of going anywhere. She tries to get some piece and quiet.

At the dig near Ur, Colonel Lifford reluctantly asks Daphne Garsington to climb through the narrow opening into the tomb to give the team points on how to better break in without damaging anything. She is a woman and not even an archaeologist, just seconded to the dig from the British Consulate, but she is the only person small enough to get through. Daphne is happy to oblige. Her not-so-secret admirer Archie Ferrers gives her a leg up, and in she goes. At first she is amazed at the wonders inside, but soon she is attacked by moving lights and is lost in the tomb.

Having learned the disturbing news on the telegraph, Professor Straiton relays it to River, thinking that now the situation is definitely out of her league. To his amazement, in five minutes she is ready for the trip. She barely makes it to a steamer sailing from Southampton to Constantinople. On the ship, she has to fend off attention of a Bertie Potts, the British Consul in Ur. He happens to know about the tomb because Daphne was sent from his consulate. He was not, however, informed about her fate.

After days of sailing, they reach their destination. When the hired driver for River refuses to take her to the tomb because of superstitions and strange sounds from a saltwater dam near the tomb, Bertie offers River his car. He is mortally bored by his consular responsibilities and needs a change of scenery. River reluctantly agrees but insists on driving herself.

Their arrival at the dig is marked by awkwardness when Colonel Lifford assumes that only a man can be a professor. River assures him that her gun gives her equal chances against any man. Turns out that most of the archaeologists have left in fear. Only Freeman Lifford and Archie Ferrers remain, the latter is desperately trying to dig a wider opening to save his beloved.

River takes over and soon their little team makes a hole sufficient for her to get through. Bertie is skinny enough to fit there too, and is naturally co-opted by River to join her. They too barely have time to contemplate the ancient treasures before Bertie is attacked by some glowing insect-like lights, which seem to be interested in tears and sweat, and then by something human-shaped, wearing Daphne's clothes and very thirsty. They manage to hide from the apparition inside the inner chamber of the tomb by operating a lever. Trouble is, it can only be operated from the outside. Worse still, River's colt remained there.

Apart from the dead king, the chamber contains many dried-up small animal corpses and human remains that soon spring to life and announce that she used to be queen Prim and now she is thirsty. River manages to learn that Prim was buried alive here in the tomb and has been staying semi-alive all this time before burning her to a crisp. River is not, however, sure that this death would be final for Prim.

Bertie manages to reach the human part of the monster-Daphne lurking outside. He asks her to operate the lever, but Daphne is too weak. By now River has figured out that the glowing flying things are saline drones, which are normally used to keep crew of spaceships alive during long trips. They collect salt wherever they can and use it to keep the crew healthy. But the ones in the tomb are malfunctioning and have been keeping Prim alive for the past 3000 years, turning her into a salt-thirsty monster.

Since River neither cries nor sweats, Bertie has to do jumps to produce enough sweat for Daphne to be able to operate the switch. But the drones are feeding Prim too. By the time, the door cracks open, Prim is attacking them again. Forgetting his disguise, Bertie laments that River did not bring her vortex manipulator. But there is no time for surprises. While River, with difficulty, keeps Prim away, Bertie squeezes under the door but makes a mistake of letting Daphne touch him. Now he is also contaminated by the malfunctioning saline drones while Daphne is strong enough to leave the tomb.

Although severely dehydrated, Bertie manages to operate the switch and let River out too. She picks up her colt and stops Prim with several bullets. The door to the inner chambers closes again. Bertie is already feeling the thirst but manages to explain to River that he was tasked with bringing her to the tomb. This whole adventure was intended as a test for her. But he would not reveal his masters. Before she leaves, he produces a letter addressed to her.

River is not fast enough to save Archie from being contaminated by Daphne. She tells Lifford that the couple are not humans anymore and they need to stop them. Meanwhile, spurred by his thirst, Bertie lets Prim out of her chamber. She restores her strength feasting on him and is finally free. To River's surprise, however, Prim does not attack. Still, whatever her plan is, River has to stop her.

She gets dynamite, tells Lifford to climb some tree and under no circumstances touch either Archie or Daphne and goes after Prim. She manages to talk to Prim, who wants revenge to all the husbands who do this to their wives. Already the infection spreads across the valley. Snakes and scorpions are infected. And there are hundreds if not thousands of human bodies buried all around. River tries to explain that Prim's husband is not to blame for what happened to her, that both River and Prim seem to be pawns in some cosmic game. But that only redirects Prim's anger to River. Still she manages to persuade Prim to jump into the saltwater reservoir on the other side of the dam. River correctly calculates that the saline drones won't know when to stop pumping water into Prim, eventually destroying her. Realising the treachery, Prim tries to drown River with her. The dynamite explodes and salt water floods the valley. Now all bodies contaminated with saline drones, dead or alive, would meet the same fate as Prim.

River is saved by Colonel Lifford who did as instructed and, luckily, had a pick she managed to hold on to. He laments that the whole dig with tomb and everything is now washed away, but River doesn't think this to be a loss to archaeology: the tribe's history was manipulated by forces unknown. She tries to minimise the damage by providing the colonel with a plausible explanation: there was an epidemic of desert sickness, with hallucinations and all. He is the only survivor. She asks him to notify the next-of-kin of Archie, Daphne and Bertie.

On the way back, she concedes that trouble would find her no matter how she hides. She is ready to pursue the mystery further by accepting the invitation in Bertie's letter, the invitation to a social event at an unspecified venue, but with temporal-spatial coordinates for pick up somewhere in the Magellan Cloud.

Cast

 * River Song - Alex Kingston
 * Bertie Potts - Alexander Vlahos
 * Daphne Garsington - Charlotte Christie
 * Colonel Lifford - Alisdair Simpson
 * Archie Ferrers - Oliver Dimsdale
 * Professor Straiton - John Banks
 * Prim - Gbemisola Ikumelo

Uncredited cast

 * Surene priest - Aaron Neil
 * Old local - Aaron Neil (all from BFX: The Diary of River Song Series One)

Continuity

 * River uses her sonic trowel. (TV: The Husbands of River Song)
 * River owns a vortex manipulator. (TV: The Pandorica Opens et al.)
 * Professor Straiton says that the tomb of Tutankhamen was discovered last summer. This tomb was found by Howard Carter on 4 November 1922 and the burial chamber was opened on 16 February 1923. (PROSE: The King of Golden Death) This places the main events of the story in 1924. Thus, the 3,000-year-old tomb originates from the 11th century B.C.
 * River mistakenly believes Bertie is trying to court her and starts to rebuff him by saying she's a married woman. (TV: The Wedding of River Song, The Angels Take Manhattan, The Husbands of River Song)
 * Bertie complains that River refused to stop the car when his hat blew off and River replies, "Hats are overrated." She has previously shown contempt towards the Eleventh Doctor's fez (TV: The Big Bang) and Stetson. (TV: The Impossible Astronaut)
 * Like other Time Lords, River has an acute sense of smell. She notes by smell alone that there are no living or dead bodies in the tomb. (PROSE: Wishing Well, Doctor Who and the Carnival of Monsters)
 * River scoffs that she is known as a psychopath. (TV: Let's Kill Hitler, The Angels Take Manhattan)
 * River says life has been cruel to her and compares her early life to being trapped in a tomb. (TV: A Good Man Goes to War, The Impossible Astronaut / Day of the Moon, Let's Kill Hitler, Closing Time, COMIC: Imaginary Enemies)
 * Bertie's invitation gave River coordinates to a port in the Magellan Cloud. (AUDIO: The Last Voyage)
 * The Bertie Potts that River meets on the steamer is a clone of the real Bertie Potts. (AUDIO: The Rulers of the Universe)