Warner Mifflin--energetic, uncompromising, and reviled--was the key figure connecting the abolitionist movements before and after the American Revolution. A descendant of one of the pioneering families of William Penn's "Holy Experiment," Mifflin upheld the Quaker pacifist doctrine, carrying the peace testimony to Generals Howe and Washington across the blood-soaked Germantown battlefield and traveling several thousand miles by horse up and down...