The condition of the slaves interested him, and in 1844 Walker aided several of them as they attempted to make escape in an open boat from the coast of Florida to the British West Indies, where slavery had been abolished ten years before.

Put on trial in federal court in Pensacola, Walker was convicted, heavily fined, and sentenced to be tied to a pillory, and publicly branded on his right hand with the letters "S S" (for "slave stealer").

United States Marshal Eben Dorr, who also traded slaves, executed the branding with a hot iron.

[1] Walker was then returned to jail, confined eleven months, and released only after Northern abolitionists paid his fine.

[citation needed] For five years after his release, Walker lectured on slavery in the Northern and Western states.

[10] A plaque commemorating Walker was erected on the lawn next to the Harwich, Massachusetts, Historical Society.