The following version of the novel was used to create this study guide: Larbalestier, Justine. My Sister Rosa. Soho Teen, November 15, 2016.

In the novel My Sister Rosa by Justine Larbalestier, Che Taylor is a typical teenager with some specific goals for himself. He is training as a boxer and wants to spar even though he has promised his parents he will not. He wants a girlfriend. He wants to go home to Australia where he lived for seven years. Most of all, Che wants to keep his sister Rosa under control. He has suspected there was something wrong with the girl since she was just an infant, but as she grows her behavior becomes more and more disturbing. His parents do not seem to notice how strange Rosa is even though she lies compulsively and enjoys killing things. Despite Che’s worries about his sister, he never thought she would seriously hurt someone until it happened one day. In the chilling end, Che struggles to come to terms with what he learns about himself and the rest of his family.

Che sits next to Rosa on the plane as his family travels from Bangkok to New York so his parents can start a new business. He describes her as looking like a doll with her dimples, blue eyes, and blonde curls. Even though she looks like a doll, Che knows she is not normal. He describes how Rosa did not develop emotionally like other children. However, she was smart enough to understand what her parents wanted from her. When they took her to doctors for a diagnosis, Rosa would learn to correct her behavior.

One of the first things that Che did in New York was to visit the boxing gym at which his grandfather, Papa, had signed him up. Che’s Papa paid for boxing lessons because Che’s parents did not want Che involved in the sport, which they believe is violent. He wishes he could develop his technique by sparring, but he promised his parents he would not do so until he stopped growing. At his gym, Che sees a black girl, Sojourner, who moves easily, the way he wishes he did. After Che meets Sojourner again in a park near his house, the two strike up a friendship. Rosa learns about Che’s friendship with Sojourner and knows that her brother is in love with Sojourner. She sneaks off to attend church when Che visits with Sojourner at her church in order to cause trouble. When talking to Che about Sojourner, Rosa threatens to push Sojourner down a flight of stairs because Sojourner likes Che better than she likes her.

Meanwhile, Rosa has struck up a friendship with Seimone, one of the twin daughters of the McBrunights, the family who is bankrolling the new business that Che’s parents are trying to start. Seimone has a peanut allergy and everyone in Che’s family is taught how to use an auto injector. One morning, Che hears Rosa laughing and fears something is wrong. The girls have made a smoothie with peanut butter. Seimone is turning blue from an allergic reaction. Rosa has the injector in her hand but is laughing at Seimone, not using it. Che takes the injector from Rosa and saves Seimone’s life. Afterward, Che confronts his father, who says he has known about Rosa for some time, about having her tested for mental illness but his father does not want Rosa labeled.

Weeks later, Che is walking with Rosa, Seimone, and Seimone’s twin sister Maya to tennis lessons. Che has noticed Rosa and Simone have been acting strangely and have insisted that they be allowed to pick the route they walk to the tennis courts. As they are waiting to cross a street, Che sees Maya fall off the curb. She is hit by a bicycle. Che had thought Maya tripped but several witnesses believe that either Seimone or Rosa pushed Maya. Rosa blames Che. At first, Maya was diagnosed with non life threatening injuries but she developed a brain bleed and died.

In light of the fatal accident, both Rosa and Che were given psychological examinations. Che hoped it would finally be determined that Rosa was a psychopath but was shocked when it turned out that his brain had the same morphology as Rosa’s. Because Sojourner realizes she could never have children with Che, she breaks up with him. Che’s father runs away when Maya is killed because he does not want other people to know he is a psychopath as well. It is determined that Seimone was the one who pushed her sister into traffic. Che believes it was Rosa who probably told Seimone to push Maya.

The McBrunights choose not to press charges against Rosa, but they insist that the family leave the country. On the flight on the way back to Australia, Che thinks about how he wished at one time he could go back home. He returns to Australia missing Sojourner and wishing he was not leaving her behind. On the plane, he sees that Rosa is wearing a ruby necklace that once belonged to Maya. He realizes that she has only been encouraged by her success with Maya’s death and that her behavior will only get worse.