In 1848 an English physician, Nathaniel Trennant, accepts an offer to serve as doctor on a ship carrying immigrants to America. When arriving in Baltimore, Trennant stumbles onto its slave market and witnesses the horrors of human bondage. One night in a boardinghouse he discovers under his bed a runaway slave. Disturbed and angered by the selling of human lives, he offers to help the young man escape, a criminal action that will put the fugitive...