A mysterious letter detailing a supposed Islamist plot to take over schools shocked Britain in 2014. But who wrote it? From Serial Productions and The New York Times, “The Trojan Horse Affair,” an investigation that became bigger than we ever imagined. All eight parts are coming next Thursday, February 3rd. To get full access to this show, and to other Serial Productions and New York Times podcasts on Apple Podcasts and Spotify, subscribe at nytimes.com/podcasts. To find out about new shows from Serial Productions, and get a look behind the scenes, sign up for our newsletter at nytimes.com/serialnewsletter. Have a story pitch, a tip, or feedback on our shows? Email us at serialshows@nytimes.com