When we left off with our second season, there were... a few things happening with Iran… And Amb. William Burns has a unique perspective -- he's been down this road with Iran before, as one of the architects of the 2015 nuclear deal. We ask Burns for a gut check on the current situation, from Iran's threats to ramp up uranium enrichment, to the fallout from President Trump's 'exchange of love letters' with North Korea. He also shares some of the lessons from "the most depressing brainstorming session" of his career. William Burns served five presidents and retired as the State Department's No. 2 official. Today he’s the head of the Carnegie Endowment for International Peace, in Washington, DC. His book is “The Back Channel: A Memoir of American Diplomacy and the Case for Its Renewal.”