Soumaya Keynes and Chad Bown have spent nearly a decade talking about trade. They started as podcast partners—nights and weekends, no advertising, holding down day jobs at the Financial Times and the Peterson Institute for International Economics, respectively—because their employers were fine with this particular side hustle.

Their origin story is, by Keynes’s own telling, a little absurd. When she was at The Economist and trying to launch an economics podcast, she auditioned several co-hosts, including Bown. They were pleased with their wonky pilot, but a colleague confided: “By the end of it, I lost the will to live.” Keynes knew she had a match. “I was like, ‘Cool, he’s the guy I want to do my podcast with.'”

Their schedule was naturally interrupted when Keynes gave birth last year and decided she needed a new project, so calling Bown was the obvious move. The result is How to Win a Trade War, their first book together. It published this spring—right as President Donald Trump boarded Air Force One for Beijing to meet President Xi Jinping—and it may be the most useful thing you can read to understand what just happened, and what comes next. As Fortune caught up with Keynes and Bown, they were backstage in New York, beaming at their forthcoming appearance with Jon Stewart on The Daily Show.