Why does Chapel run away in The Longest Memory?

Unlike his biological father Whitechapel, Chapel hates slavery with a passion. One of life's free spirits, he instinctively rebels against his captivity, realizing that if he's to be free, he's going to have to take hold of that freedom for himself. That means escaping from the plantation and heading up North to "paradise."
Chapel's loathing of slavery is not just personal, but also theoretical. Thanks to the influence of Lydia, with whom he's very much in love, he's gained a philosophical understanding of justice, with which his day to day experiences of slavery are clearly in sharp conflict.
But it's Chapel's love for Lydia which is the decisive factor in his decision to escape. He harbors the romantic notion that he and Lydia will elope to the North, where they will live together happily ever after as a free couple. Sadly, things don't work out quite like that, and Chapel is caught during his attempted escape and brutally whipped to death.