The behind-the-scenes story of the investigation that shook America to its core—the Mueller investigation that presented the evidence of Russian interference in the 2016 presidential election—as told by Robert Mueller’s closest colleagues, including never-before-revealed details into how the team investigated Putin’s campaign to favor candidate Donald Trump and Trump’s efforts to interfere in the investigation. Interference is the true history of the most important and consequential decisions, obstacles, and quandaries Mueller and his team faced when investigating Russian interference in the 2016 presidential election. For the first time, Mueller’s only deputy, his most senior counselor who served on the Watergate Special Prosecution Force, and the lead prosecutor looking into obstruction of justice and Russian interference, have come together to tell a highly relevant and readable account of what it was like to carry out their investigation of election interference, as well as any connections that existed between the Russians and members of the Trump campaign. Interference also highlights the many actions Russia took as it favored candidate Donald Trump over Hillary Clinton offering a powerful reminder of how committed Russia was to determine the outcome of the election. Ultimately, the special counsel brought indictments against thirty-four individuals and entities, including Trump’s campaign chairman; his deputy campaign chairman; a campaign advisor; his first national security advisor; and one of Trump’s longtime associates; as well as against Russian participants. Nearly every case that was able to proceed resulted in a guilty verdict or plea. Interference explains the motivations and actions of Russia (which has not stopped exploiting America’s weaknesses), the importance and the limitations of a special counsel, and the need for people to make principled decisions even when being pushed from all directions not to. Much can be learned from the experiences faced by the Mueller special counsel office as it broke ground on some of the most complicated challenges facing our country—then and now. The narrative carries special relevance today, as the Supreme Court has sharply limited the conduct by a president that can be prosecuted—or even investigated.