Each chapter switches the perspective from which it's being told. The main characters (and perspectives we hear from) are:
Anna Fitzgerald- 13 years old and knows that the reason her parents had her was so that there could be a bone marrow donor for Kate. She hires a lawyer to get medical emancipation from her parents so she will not be forced to donate her kidney.
Kate- 16 years old and older sister of Anna's. She was diagnosed with acute promyelocytic leukemia at a very young age. She has basically lived with it almost her entire life.
Jesse- Oldest child, brother to Anna and Kate. He is very rebellious, and his parents often don't know where he is at. He likes to play with matches and intentionally burns down old vacant buildings with a friend.
Brian- Father of Anna, Kate, and Jesse. His is a firefighter. Although he lives at the firehouse a lot and called away often, he is a very loving and attentive father.
Sara- Mother to the three teens. She has desperately cared for Kate since she was diagnosed. Although she clearly loves her other children, the high level of attention she gives to Kate does not give her much time to pay much attention to Anna or Jesse, almost to the point of being callous.
Campbell Alexander- He is the intelligent, savvy attorney Anna hires. Caring little about anyone else, he takes on Anna's case because it will bring him a lot of publicity and he doesn't think he'll have to do much work to win the case. He has a service dog, although we don't find out until the end what it is for.
Julia Romano- She is the guardian ad litem for Anna. She dated Campbell when they were both in high school and they both had strong feelings for each other, and those flames are rekindled when they see each other again afters an number of years.
The book starts off with Anna selling some of her belongings in a pawn shop. After going home she goes to the office of Campbell Alexander in order to hire him to sue her parents "for the right to [her] own body." The reason her parents had her in the first place, she explains, was so that she could donate bone marrow to her older sister. But over the years she has had to go through more and more surgeries. And now, her parents want her to donate a kidney to Kate, Anna has never had to donate a body organ before. Once Campbell realizes that she is very serious about what she is doing, he agrees to be her lawyer, pro bono, knowing he'll get a lot of publicity from the case. He is going to demand medical emancipation for Anna.
Anna's parents are shocked when they receive the legal papers informing them of what Anna is doing. When they realize that they are going to need a lawyer, Sara, who is a lawyer, decides to be the lawyer representing the opposing side, not really believing the case will go far and thinking she'll be able to talk Anna out of the suit. She thinks Anna is only doing this for attention. Campbell makes it clear in court that he wants Anna out of the house since her mother is opposing counsel. The judge appoints a guardian ad litem for Anna, Julia Romano, her job is basically to represent the best interests of the minor child.
Through out the book we see that Anna feels guilty about the decision she has made and questions it. She doesn't want to hurt her family. Campbell becomes very agitated at Anna's reluctance. He goes through his own turmoil, having to work with an old flame. It comes out during the trial that his service dog is meant to warn him when he is about to have seizures. Turns out that Campbell got into a car accident at 18 and suffered permanent seizures from it. He left Julia because he didn't want to burden her with his affliction. When Julia finds out she begins to forgive Campbell for what he did, and they start a relationship again.
Brain finds out that Jesse, his son, has been the person starting all of the recent fires he and his men have been putting out. Confronting Jesse, the boy admits that he feels immense guilt due to the fact he wasn't a donor match for Kate. Brian realizes that Jesse psyche worked to convince him that since he couldn't rescue, he had to destroy.
From Sara's perspective, which is told from the past, starting from when Kate was diagnosed, to the present story. We see throughout her perspective that everything she did was always out of love. However, it seems that she did pay too much attention to Kate to the point of emotionally neglecting her other children. Kate was always her first concern and she didn't think much about that and considered it a given since Kate was dying. Through out the trial and book, Sara realizes where she went wrong in some aspects of her parenting. Though she is frustrated at what Anna is doing, she never hates her or stops loving her for it.
Right before the end of the trial, a plot twist: When Anna first found out about the need for a kidney transplant, she was going to do it and had not problem with it. But, Kate convinced her not to. Turns out, she didn't want to go through with the surgery, she was sick of it all. She knew she'd die without the transplant, but she just couldn't go through it all. It was Kate who convinced Anna to get a lawyer.
The trial ends with the judge ruling in Anna's favor. She receive medical emancipation from her parents. Everyone is happy that the case is over, and no one is mad at Anna for doing what she did.
A sad twist of fate then happens. Campbell is driving in a car with Anna in the passenger seat. The car is struck by a truck. Campbell makes it out okay, but Anna is left brain dead. Everyone is stricken with grief, especially Sara who had always been planning out the death of her other daughter, Kate. The doctor asks about organ donation. Campbell, being the medical power of attorney for Anna, says that Anna would want her kidney donated to her sister.
Epilogue: Told for the first time from Kate's perspective, she talks about what happened to her family in the few years after Anna's death. The transplant worked and it has been 8 years since her last relapse. Sara suffered from a heavy grieving process. Brain overcame alcoholism. Jesse became a policeman. Julia and Campbell got married. It ends with Kate explaining that with the transplant she takes Anna with her, not matter where she goes.