But on "Serial," we’ve heard the style of "This American Life" style gone slack and meandering. The first episode, which hooked listeners, found Koenig amazed and astonished that her subject, a convicted murderer whom she meets in a Maryland prison, could be such a nice, presentable and well-spoken guy. To his credit, the guy refrains from telling Koenig how naïve she is. (He’s been in prison a while, so perhaps he’s inclined be patient with visitors, no matter how silly they are.)

Some background: Adnan Syed and Hae Min Lee were high schoolers in 1999, sweethearts until shortly before Lee’s disappearance. She was found dead, six weeks later in a suburban park. Syed was convicted largely on the testimony of a friend, Jay, who told police that Syed asked for help in concealing Lee’s body; Jay pleaded guilty to being an accessory after the fact. Koenig never manages to score an interview with Jay, the detectives who cracked the case, or Lee’s family.

Koenig does locate various classmates of victim and convict. Some gossip, some refuse to talk. There has to be an hour of chatter between Koenig and her producer, musing about those interviews that got away. So much musing that it becomes difficult, at times, to separate fact from supposition. As Koenig likes to say, "More on that later...," as though she’s leading into a advertising break. "Serial"’s crossover audience appeal is remarkable; I’ve heard it discussed by everyone from older literary-minded listeners familiar with "In Cold Blood" and other New Yorker magazine crime writing to 20something listeners who wouldn’t be caught dead watching CBS’s "48 HRS" or the more lurid "Dateline NBC." The medium—longform podcast—may be new, yet that doesn’t make "Serial" better.

What does "Serial" serve up? Gut feelings. Koenig starts with a hunch and more or less stops there. "My interest [in the story]...," she says. "Like, you’re a really nice guy." Even Syed grows weary of that angle. "To be honest with you," he tells her. "I feel like I want to shoot myself, If I hear someone else say, "I don’t think he did it because you’re a really nice guy."

Which is the greatest moment in "Serial."

Less convincing, though, are Syed’s sort-of acquaintances, who step forward after 15 years to provide dubious alibis. (Right. And these helpful alibis-come-lately cannot possibly be contaminated by media accounts or ulterior motives on the part of the tellers. These people, like, forgot to say anything back when it counted.) "Serial"’s like a National Geographic Radio Expedition about capturing vocal fry in the wild.