"The Passing of Grandison" starts with a conversation between Dick Owens and Charity Lomax. Charity tells Dick that if he did something she considered heroic, she could be convinced to fall in love with him and marry him. For this reason, Dick decides to help one of the slaves of his father's plantation to escape to the North. He chooses this particular way to impress Charity because she admires the courage of a man from Ohio, who tried to help another man's slave gain freedom but was unsuccessful and, as a consequence, was jailed. The man died of a disease shortly after being imprisoned.
To achieve freeing one of his father's slaves, Dick decides to go on a trip north and take his slave Tom along; he is convinced Tom will use any opportunity to escape and Dick will achieve his goal very easily. However, Colonel Owens, Dick's father, is opposed to his son's being accompanied by Tom as he is convinced that the slave will escape and constitute a property loss. Instead he suggests that Dick take Tom's brother, Grandison. He suggests that his son ask Grandison about his status as a slave to ensure that he is trustworthy and will not try to escape.
Dick takes Grandison with him to New York City and Boston, and then to Niagara Falls, New York, where he even crosses to the Canadian side. (Great Britain had by then abolished slavery in Canada and other colonies in the Western Hemisphere.) Despite having numerous opportunities to escape, Grandison does not run away and refuses abolitionists' attempts to persuade him to flee into freedom. Dick decides to have Grandison kidnapped to get him out of view in order to appear to have helped the slave gain freedom when he reports back to Charity.
Four weeks after Dick Owens' return to his father's plantation in Kentucky and one week after his marriage to Charity Lomax, Grandison returned to the property. He was welcomed and celebrated as a loyal slave, as he confirmed Colonel Owens' positive understanding of slavery. The colonel gave Grandison a place as a house servant.
After about three weeks, Grandison and his family (his new wife, his parents and his three siblings) go missing. Colonel Owens' view on slavery is shaken when he discovers the slaves have escaped. He searches for the fugitives and last sees them on a small steamboat crossing Lake Erie toward Canada, where they will be free.