I've been doing a little research on Massachusetts history and I came upon the name Shadrach Minkins. Minkins was a slave who escaped from Virginia and made his way north to Boston around 1850. He got work there as a waiter.
With the passage of a more stringent Fugitive Slave Law, in 1850, federal agents were allowed to seize escaped "property." An older Fugitive Slave Act passed by George Washington in 1793, left enforcement up to individual states. In states like Massachusetts, which had outlawed slavery, enforcement was ignored.
So, with the new law in effect, federal agents captured Minkins at his place of employment and took him to the court house. Boston abolitionists made their way past guards, into the courtroom, and carried him away. After being hidden in an attic, Minkins was taken to Canada by way of the Underground Railroad.
That's the condensed version of the story. I hope to learn more some day--I'll add it to my list of "things to look into." If anyone else finds the story intriguing, there's this book on the subject, Shadrach Minkins: From Fugitive Slave to Citizen by Gary L. Collison, published by Harvard U. Press.