The Times obtains Donald Trump Jr.’s emails about an offer of help from the Russian government. “I love it,” he wrote. The story behind the story, and what we mean when we talk about “collusion.” And the scene from the Iraqi city of Mosul: What Islamic State militants left behind. Guests: Matt Apuzzo, one of the reporters who broke the story about Donald Trump Jr.’s emails; Rukmini Callimachi, who covers the Islamic State, and Andy Mills, a producer with her in Mosul. For more information on today’s episode, visit http://nyti.ms/2sPxzbb.