The ink was still drying on special counsel Robert Mueller’s appointment papers when his chief deputy, the famously aggressive and occasionally controversial prosecutor Andrew Weissmann, made a bold but secret overture in early June 2017. Weissmann quietly reached out to the American lawyers for Ukrainian oligarch Dmitry Firtash with a tempting offer: Give us some dirt on Donald Trump in the Russia case, and Team Mueller might make his 2014 U.S. criminal charges go away. The specifics of the never-before-reported offer were confirmed to me by multiple sources with direct knowledge, as well as in contemporaneous defense memos I read....