It’s been 12 years since social worker Cassie discovered a mysterious mould in her home, invisible to almost everyone except her. Now the fungus has spread - its glowing spores a major global health threat, infecting the brains of those who inhale them. But many refuse to take seriously a menace they cannot see.

When spores erupt at a care home in Wales, Cassie’s son Bryn and 30 residents are exposed to infection. But how could this have happened when just days earlier the building was declared mould-free by a mycelium-sighted Inspector?

For Bryn there is only one explanation - not everyone who claims to see the mould can be trusted. But who is this rogue Inspector and why would they lie? In his search for answers, Bryn’s fraught relationship with Cassie will be tested to the limit as they battle to stop the fungus before the looming pandemic can take hold.

In Greek mythology, Cassandra was condemned to speak the truth yet never be believed. A story of trust and what happens when we lose it. And of a hidden threat destroying the very thing that makes us powerful.

By Marietta Kirkbride

Cassie ….. Kate O’Flynn
Bryn ….. Ben Skym
Pascal ….. Emmanuel Berthelot
Ola ..… Aggy K. Adams
Helen ….. Laurel Lefkow
Ethan ..... Philip Desmeules
Josie ..... Cristina Wolfe
Aditi Saklani ..... Amrita Acharia
Conference attendees ..... Laila Alj, Liis Mikk

Bonobo recordings courtesy of Professor Zanna Clay of Durham University

Production Manager: Eleanor Mein
Production Assistant: Liis Mikk with Teresa Milewski

Executive Producer: Sara Davies

Title music: Ioana Selaru and Melo-Zed
Track laying: Andreina Gómez
Sound design: Jon Nicholls and Adam Woodhams

Directed and produced by Nicolas Jackson

An Afonica production for BBC Radio 4