Hello! Although the novel doesn't fully expound on how Curzon gets sent to jail, Chapter 34 starts out with Isabel telling us about a party to celebrate the capture of Fort Washington, complete with turtle soup. Now, what's important about Fort Washington? In Chapter 33, a serving girl tells Isabel that there was a battle 'up the fort,' where 'Hessians killed lots.' The Battle at Fort Washington was a real battle of the American Revolutionary War. It was fought on November 16 of 1776 (you will notice that Chapter 33 is dated from September 27, 1776 to November 16, 1776).
The Hessians were German soldiers who aided the British in the fight. It was a decisive British victory, and almost 3000 American soldiers were captured. The novel bears out this historical fact:
"So, how many rebel prisoners did your men bag, Colonel?" asked Master Lockton.
The colonel shook his head. "Near three thousand of the devils. Wish we could have shot them all."
Although Curzon is a fictitious character, the battle of Fort Washington really did occur. Curzon also likely represented the many African-American slaves who fought for their own independence from slavery in order to have a chance to live in an independent America. If you think about it, that's nothing short of amazing. Curzon ends up in jail for fighting on the side of the Patriots in the Battle of Fort Washington; he tells Isabel that he saw things during the battle that are 'not fit for the eyes of any person.' His anguish mirrors the real anguish experienced by all the patriots who really fought for American Independence more than 200 years ago.
Hope this helps explain things. Thanks for the interesting question!