Hosts of the Wirrn (audio story)

 was the first story in the audio anthology, Revisitations, produced by Big Finish Productions. It was written by Chris Chapman and featured Jemma Redgrave as Kate Stewart and Ingrid Oliver as Petronella Osgood, James Joyce as Josh Carter and Ramon Tikaram as Vikram Shindi.

Part one
After the world's strangest interview, UNIT's latest recruit, Shana Siddiqui, hits the ground running to help Osgood with her latest assignment.

left UNIT a parting gift – something alien and deadly. The Wirrn have come to Earth, and now they are free...

Part two
Larvae are hatching. Grubs are mutating. The infection is spreading. As a swarm takes to the skies, UNIT struggles to contain its menace.

Kate Stewart meets the danger head-on. To rid the Earth of the Wirrn, she must now confront their Queen.

Part one
Holding a case containing an egg left behind for UNIT by, who took it from the Auctioneers' collection at the Whitehouse Gallery, Osgood flies to Kate and Shindi with Josh and Sergeant Brundle when they hit turbulence. The case opens and Brundle touches the egg, causing him great pain. The helicopter crashes and Brundle emerges from the wreck saying "Wirrn". Deeming it too late to save him from his infection, Shindi orders his men to shoot him.

Osgood surprises Shana Siddiqui by interviewing her to join UNIT as an entomologist via a remote-controlled raven and offers her the job. Shana resigns as a researcher and heads to Lake Windermere where, after mentioning the code word "Skarasen", she is directed to the Well, a secret bio-research facility beneath a hut. Josh gives her a brief tour and, after receiving a welcome from Kate, who appears from Geneva as a hologram, Shana joins Osgood and Josh in descending to the bottom of the Well in a hazard suit and is decontaminated several times.

Having survived UNIT's bullets thanks to his new hide, Brundle is at large and being hunted by Shindi, Private Sedgwick and Private Jack Evans. Evans finds him in the forest and is killed, his body later being found by Shindi and Sedgwick next to a tunnel burrowed by Brundle. Shindi informs Kate, who is heading back from Geneva.

Shana is amazed by the Wirrn egg, which Osgood is simultaneously fascinated and disgusted by and has named Elizabeth due to her belief that the egg is that of a Wirrn Queen. Shana is given keys to a flat that she is to share with Kirsty Musgrave, a former UNIT field medic who now works at A&E. The following day, Kate and Osgood discuss Brundle and deduce that his purpose is not to infect others but to protect his Queen. Shana analyses cell samples taken by Marcus, the tech specialist, and the sample bites its way into her hazard suit. When Osgood notices the damage, Shana lies and says that it caught on a door.

Putting on a new hazard suit at Osgood's order, Shana finds that she has a build-up of green tissue around her wound with a texture like tiny bubbles. She gets the idea to stimulate the egg to hatch with small electrical charges, a plan which Osgood implements with success. The Queen hatches and, given that she has a mental link with Brundle and is fluent in English, Kate tries to communicate with her and receives only roars as a response. In private, Shana calls Kirsty and tells her that she is unwell, but the voice in her head tells her not to talk to Osgood about it despite Kirsty's insistence.

Shindi and Sedgwick chase Brundle, who attacks Sedgwick and declares that the Queen has been born. Shindi accidentally kills him with an electro-shock rifle and he informs Kate, who says that it will not help negotiations with the Queen. The Queen is released from her cage by Shana and stings Marcus before Shana puts the shield back up to stop her leaving. Kate, Osgood, Josh and Shana put him in a quarantine pod and determine that he has twelve eggs inside of him, growing surprisingly quickly. Shana keeps the truth of what happened secret.

Kate speaks briefly with Marcus and orders Josh to review the video feed of his stinging and to bring Shindi. Marcus persuades Shana to free him from the pod and his electro-restraint with her retina and to take him to the Queen. Osgood finds them in the lab as Marcus prepares for the eggs within him to hatch before their Queen.

Part two
The Wirrn grubs emerge from Marcus and Osgood realises that Shana has been under the Wirrn's influence. After shutting the lab down, Osgood uses mechanical arms to kill some of the Wirrn whilst Kate sends Josh down to assist, hesitant to activate the self-destruct. Marcus uses Shana's codes to free the Queen and the Wirrn go on to slaughter Josh's men until he activates the decontamination process to slow them down. Osgood realises that Shana can be a spy for either side and helps her hold onto her own identity in a containment field.

With Osgood, Josh and Shana out of the way, Kate attempts to activate the self-destruct sequence but finds that it has been permanently disabled thanks to Marcus. The Wirrn get to the surface by burrowing to the lakebed and kill the fisherman and his dog before heading to the town, which Kate puts under quarantine. Shindi goes to the hospital and helps Kirsty search for the infected Jacob Lester, who has been taken over by the Wirrn and infects the patients in intensive care. Shindi and Kirsty evacuate the hospital as the Wirrn attack.

Shana starts to give into the shared Wirrn mind and begins full metamorphosis, so Osgood administers tranquilisers to help with the pain. The Wirrn speak through Shana and tell Kate to go to Windermere to enter into negotiations with the Queen. Kate is led by Marcus to the war memorial where the Queen, now twenty foot tall, stands. The Queen asks for Windermere as a home for the Wirrn, but Kate refuses and asks her to leave Earth forever. As the Queen begins her war against humanity, Kate is saved by Josh and pursued by flying Wirrn in his helicopter until Osgood flies the robotic ravens into them.

Kate asks Shana to access the shared Wirrn mind and find out what disaster the Queen was the sole survivor of. Shana dives into Wirrn history and learns that the previous Queen absorbed a mammal carrying a virus which killed her and, because of her psychic connection to her children, they all died. Osgood injects Shana with a virus from the cryo-archive which kills the Queen and those that she and her children infected, but Shana is saved by UNIT's antidote. Kate feels responsible for all of the deaths, which are to be covered up as the result of a viral outbreak.

Shana remains at the Well and appears as a hologram recreating her original body rather than letting people see her true appearance, which is now that of a Wirrn. Kate apologises to her for what has happened to her and Osgood promises to work to make her new life as normal as possible. UNIT look after their own and Shana, not being the first alien in its employ, is very much part of the UNIT family.

Cast

 * Kate Stewart - Jemma Redgrave
 * Osgood - Ingrid Oliver
 * Colonel Vikram Shindi - Ramon Tikaram
 * Captain Josh Carter - James Joyce
 * Shana - Vineeta Rishi
 * Sergeant Brundle / Simon / Fisherman / Jasper / Computer / Lift - Roger May
 * Marcus / Evans / Jacob / New Fisherman - Glen McCready
 * Kirsty / Private Sedgwick - Katherine Senior

Uncredited

 * Voice of the Wirrn - Vineeta Rishi (BFX: Revisitations)

Continuity

 * left UNIT a Wirrn egg taken from the Auctioneers' collection at the Whitehouse Gallery as a parting gift. (AUDIO: Master of Worlds)
 * The Well contains strains of the Silurian plague and the Green Death. (TV: Doctor Who and the Silurians, The Green Death)
 * The Skarasen under the lake is mentioned. (AUDIO: The Zygon Who Fell to Earth)
 * Osgood wears a stick of celery to warn her of Praxis gas. (TV: The Caves of Androzani) Josh mentions that it is a change from cat badges. (TV: The Twin Dilemma et al. )
 * Osgood mentions Harry Sullivan's files on the Wirrn. (TV: The Ark in Space)
 * Osgood suggests Kate could "send a raven" as a means of communication, a reference to the show Game of Thrones. (COMIC: The Dragon Lord)
 * Shana compares the robot arms in the Well's lab to the power loader manned by Ripley in the film Alien. (PROSE: Birthright, TV: Last Christmas, et al.)
 * Marcus notes Josh Carter "stinks" to the Wirrn due to his Auton physiology. (AUDIO: Bridgehead, Armageddon)