Daryle Williams was emotionally torn, pushing the decision right up against deadline. As a history professor at the University of Maryland, Williams had been researching the slave trade in 19th-century Brazil when he came upon two newspaper ads featuring runaway Africans. One mentioned a mother, Sancha, escaping with her two sons — Luis, 9, and Tiburcio, 4 — in 1855. The other referenced a young woman, Theresa, who fled with her nursing daughter, in 1842.