On the surface, Guantánamo Bay may seem like an unlikely target for Sarah Koenig, Julie Snyder, and the Serial team, still principally remembered for spectacle generated from the first season’s real-time true-crime reporting on the case of Adnan Syed. But as Koenig notes in the introduction of season four, this is a story they have been trying to pull together for almost as long as the podcast has been around. “Even as Guantánamo faded as a topic of national discussion...