Curzon is a huge help to Isabel in a lot of ways throughout the entire book, but he first broaches the subject of helping her obtain freedom in chapter 6. This is the chapter that has Curzon guiding Isabel to the Tea Water Pump. In addition to helping her find her way there, he also secures some much needed food for Isabel.
As friendly as Curzon is to Isabel, I can't say that Isabel is as friendly back to Curzon; however, that is to be expected. She has just lost her freedom, she and Ruth are in completely foreign territory, and the Locktons are horrible owners. Isabel has already been struck once at this point in the story. Curzon knows that the Locktons are awful people, and he's even more against them because they are "dirty Loyalists." Curzon will eventually ask Isabel if she feels "beholden" to the Locktons. Isabel says that she's just biding her time until she can find the lawyer that will grant her the legal freedom originally promised to her; however, Curzon says that he might have a quicker and more dependable solution for obtaining her freedom:
You might be better served if you placed your loyalty with us.
Isabel isn't immediately in support of doing anything for Curzon, but she does ask who "us" is and what she could possibly do. Curzon explains that Isabel is likely to hear things in the Lockton household. Isabel quickly understands that Curzon is asking her to spy, and Isabel doesn't see any good coming of that. Curzon then explains that Colonel Regan could help get Isabel's freedom paperwork straightened out as a reward for helping the Patriots. Isabel likes the idea; however, she simply isn't willing to risk herself or Ruth at this point in the novel.