Isabel has got wind of a dastardly plot. Her Loyalist—that is to say, pro-British—master, Elihu Lockton, is planning to bribe the rebel troops with a large sum of money he has hidden away in a chest. Isabel decides to tell the news to Curzon, Bellingham's slave.
On the face of it, this sounds like a fairly simple task. All Isabel has to do is run straight to the shed behind Bellingham's house where Curzon lives, tap on his window, tell him the news about Lockton, and then hurry back home. As it's nighttime, almost everyone will be asleep, so it's highly unlikely that Isabel will be caught.
But in actual fact, it's a lot more complicated than this. In New York, a city occupied by the Continental Army, there are soldiers everywhere, and Isabel somehow has to avoid them if she's going to deliver the news to Curzon. The fact that it's dark also makes it harder for Isabel to find her destination.
Eventually, however, she makes it. She tells Curzon about everything that she's seen. Curzon tells Isabel to go home and get some sleep and promises to relay her news to Master Bellingham in the morning. He expects that Lockton will receive a visit from the Committee the next day.