Warning: spoilers follow for the end of the first season of Serial The true-crime podcast Serial, which published its season finale Thursday morning, may be a 2014 phenomenon — but, though the 12-episodes-one-story format may have been new for that style of podcast, it’s actually one of the oldest tricks in the radio book. The idea of publishing a story a little bit at a time is often traced back to Charles Dickens, so when radio became the popular medium of choice in the early 20th century, the benefits of hooking an audience with the drip-drip of a story were already well known.