The conversation at a London bar in September 2016 took a strange turn when the woman sitting across from George Papadopoulos, a Trump campaign adviser, asked a direct question: Was the Trump campaign working with Russia? The woman had set up the meeting to discuss foreign policy issues. But she was actually a government investigator posing as a research assistant, according to people familiar with the operation. The F.B.I. sent her to London as part of the counterintelligence inquiry
