In 1830, David Walker sewed a pamphlet into the lining of a coat. The volume was thin enough to be hidden, but its content was far from insubstantial. At the time, many members of the US government considered this pamphlet to be one of the most dangerous documents in American history. But what was this incendiary document? And who exactly was the man who wrote it? Keenan Norris investigates. Lesson by Keenan Norris, directed by Tomás Pichardo-Espaillat.