A mysterious letter detailing a supposed plot by Islamic extremists to take over schools shocked Britain in 2014. But who wrote it? From Serial Productions and The New York Times, “The Trojan Horse Affair” is a mystery told in eight parts. Here’s the first. Find the series wherever you get your podcasts. Subscribe today at nytimes.com/podcasts or on Apple Podcasts and Spotify. You can also subscribe via your favorite podcast app here https://www.nytimes.com/activate-access/audio?source=podcatcher. For more podcasts and narrated articles, download The New York Times app at nytimes.com/app.