Today, we head to Baker Street. But not in Victorian alleyways. We are off to Nairobi to meet an extraordinary plastic detective who will take us on an extraordinary journey. From bathroom sinks to the summit of Everest, one scientist's detective work rewrote what we know about pollution. Dr. Imogen Napper discovered three million microbeads in a single facial scrub - sparking a worldwide ban. She found microplastics in the pristine snow atop the world's highest mountain. She traced pollution through sacred rivers and into Earth's orbit itself.

But here's the thing: She didn't become paralysed by the scale.

In this episode, we talk to the world's leading plastic detective about the hidden war against invisible enemies, the unexpected connections between ocean debris and space junk and why the most powerful solutions are the most boring. She also reveals what it means to stay hopeful when everywhere you look is contaminated - and why that matters more than ever. Tune in as we discover the rebels, visionaries and changemakers who are turning the tide. Available wherever you get your podcasts.