Zoe is not at all pleased when her mother wakes her up, all but throws her in the car, and dumps her at Twin Birch. It's not a hospital, it's not a jail, but the six girls who are there have very strict rules they need to follow, especially when it comes to food and "sharing" with the other patients. Zoe doesn't need to be at Twin Birch; she tries not to fight against the counselors when she has to do therapy sessions, she eats what she is supposed to even though she can tell she's gaining weight, and she hopes that she can leave soon. In order to cope, she writes letters to her best friend Elise, and talks a lot about the food rituals the two develop as well as the problems that they faced in high school. There are problems at Twin Birch as well, and gain, Zoe does not feel that her problems are severe enough to require her to be in this expensive facility. There are parts of her past that she is ignoring, and until she comes to terms with these, she won't really be healed.
This is a very good book about anorexia, and I especially appreciated that Zoe was NOT in very bad shape. I think there are a fair number of girls whose anorexia can be dealt with before they really endanger themselves. While more extreme examples are shown in the other patients, Zoe's thought processes are a valuable addition to the canon of eating disorder fiction.