A little over a year ago, Elon Musk made the world’s most expensive impulse purchase. His reasons for buying Twitter were murky at best, but in the story he tells now, he’s saving civilization. In the final episode of this season, we look at Twitter today, inside Elon’s fantasy. What happens when...

Twitter employees had always imagined the platform would be used for social good. Their idea was that free expression on the internet would lead to good things. But after the 2016 U.S. election, that notion would be put under stress. And Twitter would have to grapple with the question: what...