A 15-year-old murder case is now riveting the nation.

The attention doesn't come courtesy of a new TV series or movie, or anything involving a screen, for that matter, but a free podcast called “Serial,” a nonfiction story from the producers of “This American Life” that unspools week by week over the earphones of an unusually broad and fervent audience.

Jason Reitman, a filmmaker whose credits include “Up in the Air,” is so obsessed, he taught himself the show’s disquieting piano score while biding time between installments. “I look forward to every Thursday in a way that I don’t remember awaiting the release of an episode of anything recently,” he said. “There’s something very intimate about someone telling you a story that close to your ears.”