The Black Cadre live among us. Over a hundred-year period, this sect of the shape-shifting Zygons has been infiltrating human society. And their influence spreads across the globe... 

Transformation, the second box set in the audio drama series Zygon Century, comprises three new tales set across this century-long project, which reveal how far-reaching the Black Cadre’s schemes have become. From Munich to Death Valley to Moscow, the Zygons are everywhere. 

As new characters join the fray, Transformation also continues several stories begun in last year’s first volume, Infiltration. First, Jonathan Rigby returns as Herbert Scott, paranormal investigator, alongside horror stalwart James Swanton as the poet Anthony Poole. 

Then, Charlie Russell (the star of Mischief Theatre’s Play That Goes Wrong series) is back as Vorvoren, a Zygon on the run who has an encounter with the Master (Eric Roberts). And finally, the Third Doctor (Tim Treloar) teams up with British agent Caldwell (Joshua Manning) for a mission into Soviet Russia. 

The Worlds of Doctor Who – Zygon Century: Transformation is available to purchase now for just £19.99 (download to own) or £29.99 (download to own + collector’s edition 3-disc CD box set), exclusively here. Please note: the collector’s edition CD box set is strictly limited to 1,000 copies and will not be re-pressed.   

The three new audio episodes featuring the shape-shifting invaders are: 

1922: The Black Cadre by Jonathan Barnes 

From Munich to Dublin to an asylum in Dartmoor, the Zygons have agents everywhere, and their plans are growing in scope and ambition. 

Can Herbert Scott, that long incarcerated investigator of the occult, do anything to stop them? Is his rescuer – the German heiress, Ilse Lange – all that she seems? And why are the Black Cadre so interested in a mysterious carnival, travelling the wilder reaches of the Cornish coast? 

1968: An Incident in Death Valley by Lauren Mooney & Stewart Pringle

Fleeing her brutal human captors, and in hiding from the Black Cadre, the Zygon Vorvoren arrives at a run-down diner in the bowels of Death Valley. There, she finds a friend in Junie, a young waitress, and a town terrorised by a ruthless cult. 

But just who is their mysterious leader, ‘The Arkon’? And could he really hold the key to Vorvoren’s liberation and revenge? 

1974: The Caldwell Restitution by Ken Bentley 

Agent Caldwell has been posted to the British Embassy in Moscow and ordered to investigate a rising star of the Communist Party. But Caldwell is a shadow of his former self, plagued by nightmares of the past and misty visions of the future. 

As the Third Doctor enters the fray, human and Zygon plots collide, and Caldwell’s visions threaten to endanger the world. Though neither man can remember the other, can the Doctor and Caldwell put a stop to the Zygon Century, once and for all? 

Actor Jonathan Rigby describes his character, Herbert Scott: “In the previous volume, he was in his prime, as a rather equivocal, slightly dodgy occult investigator. Now he’s been banged up in the asylum and we meet him again 21 years later. Because of his experience with the Zygons, he is unchanged physically, but of course he’s had a very distressing 21 years. The disorientation of suddenly being back in the world is a fascinating part of the story.” 

Charlie Russell, who returns as the Zygon Vorvoren, said: “I’m so happy to see her development. She’s seen the worst of the human race, the really sharp end of that stick, and it’s hardened her and made her less trusting, but also still vulnerable. And it was so exciting to meet the Master. He brings out of her the fact that she is so angry and full of desire for vengeance.” 

On the Third Doctor’s Zygon Century debut, Tim Treloar said: “The Zygons have infiltrated the Soviet Union’s nuclear power capacity so the Doctor’s there to give a hand. There’s very much a James Bond vibe going on. I love the fact it’s set in the 70s at the height of the Cold War. Caldwell and the Doctor are a bit of a double act, on disagreeable terms!” 

The guest cast of Zygon Century: Transformation also includes James Gaddas, Toby Longworth, Duncan Wisbey, Branko Tomović, Deirdre Mullins, Nina Georgieff, Abigail Thaw, Jo Herbert, Joanna Monro, Paige Levy, Brooke Bazarian, Tom Alexander, John Chancer, Jonathan S Powell, and Leonie Schliesing. 

The Worlds of Doctor Who – Zygon Century: Transformation is available to purchase now for just £19.99 (download to own) or £29.99 (download to own + collector’s edition 3-disc CD box set). 

All the above prices (including pre-order and multibuy bundle discounts) are fixed for a limited time only and guaranteed no later than 31 May 2026. 

Please note that Big Finish is currently operating a digital-first release schedule. The mail-out of collector’s edition CDs may be delayed due to factors beyond our control, but all purchases of this release unlock a digital copy that can be immediately downloaded or played on the Big Finish app from the release date.