In chapter 17 of The Devil's Arithmetic, Gitl informs Hannah/Chaya that she and some of the others are planning to escape. She is told that Yitzchak and Shmuel are in on the plan and that they want Chaya to know about it because she is their "only flesh and blood." If something goes wrong with the escape, Gitl wants Chaya to remember them, because she is their only remaining link with the past.
When Chaya asks for details of the plan, Gitl tells her that she can't share it with her. She does not want to risk Chaya accidentally letting the information slip. Chaya swears that she would never betray the plan under any circumstances. However, Gitl wants to be as safe as absolutely possible. Consequently, she tells Chaya that she will not share the plan with her. When Chaya asks when they plan to make their escape, Gitl simply tells her that she will know when it happens.
A number of days go by before Gitl finally tells Chaya that it is time to put the escape plan into action. Even though she knew that Gitl and the others were hatching a plan, Chaya is still caught by surprise. Gitl, Yitzchak, and Shmuel had been so careful to hide their plans that Chaya had seen no signs of what they were up to. It is only at this point that Chaya is told that she is also part of the escape plan.