HARI SREENIVASAN:

It's a huge hit in the world of podcasting, garnering five million downloads on iTunes, far more than any other podcast in history.

But the idea of a serial is as old as Charles Dickens, who experienced wild success with "The Pickwick Papers" in the mid-1800s. The notion of podcasting stories has gained steam in recent years, with popular ones such as "This American Life," which has about a million downloads a week, and "Planet Money."

Less-well-known ones draw smaller audiences, but still have substantial followings. In fact, last year, Apple reported that subscriptions to podcasts through iTunes reached one billion.

RawVoice, which tracks 20,000 shows, said the number of unique monthly podcast listeners has tripled to 75 million from 25 million just five years ago.

We have only scratched the surface of the obsession some have with "Serial." It's inspired fan clubs, academic and legal inquiries, blogs and, yes, more podcasts about the podcast.

David Haglund is a senior editor at Slate and edits its Culture Blog and is a regular panelist on slate's podcast about "Serial."

So now we are having a TV conversation with a man who has a podcast about a podcast.

So why is there this fascination with just one story?