Josie introduces herself to the reader: she’s 17, lives in Sydney, Australia, and is in her final year of school at a prestigious Catholic girls’ school called St. Martha’s. She’ll take the tests for her High School Certificate (HSC) at the end of the year and then plans to study law and become a barrister. She’s her school’s vice captain and believes herself to be unpopular, in part because she’s Italian, illegitimate, and attends St. Martha’s on a scholarship. Though Josie vows to be a “saint” for her final year of school, this flies out the window on the first day when Sister Gregory catches Josie reading a Hot Pants magazine during religion class. Later that evening, as Josie and her single mother, Mama, have dinner, Mama reveals that Josie’s long-lost father, Michael Andretti, is back in Sydney for the year; he’s been in Adelaide since just after Mama became pregnant with Josie at age 17. He doesn’t know Mama went through with her pregnancy.
Sydney holds its annual Have a Say Day, where students from schools all over the city come together to “gripe” about things. St. Martha’s school captain, a wealthy girl whom Josie calls Poison Ivy, gets to ask the Premier questions on national television. But as a vice captain, Josie has to give a speech to a bunch of students. She hates it—until she realizes the boy she’s sitting next to, Jacob Coote, is extremely attractive. After school Josie goes to visit her grandmother, Nonna, which she does nearly every day. Josie hates this arrangement because Nonna is old, vain, and constantly scolds Josie for being disrespectful. Josie also resents Nonna because when Mama got pregnant years ago, Nonna and her husband, Nonno, kicked Mama out. Nonna and Mama only reconnected once Nonno died a decade ago, and their relationship is still fraught.
When debate season starts up, Josie is thrilled at the prospect of spending time with John Barton, a rival whom Josie is secretly in love with. But when they talk after their first debate, John reveals that he’s feeling depressed and possibly suicidal. His father wants him to go into law, but John doesn’t want to. A week or so later, Josie goes with her friends Sera, Anna, and Lee to the first regional dance. She hopes John will ask her to dance but ends up dancing with Jacob all night. Jacob takes Josie home on his motorcycle afterwards.
At a family barbecue that weekend, Josie comes face to face with Michael Andretti for the first time. She first overhears him telling Mama that Josie is an unwanted “complication” in his life. Josie also notices that Nonna seems to put it together that Michael is Josie’s father. When Josie corners Michael in Nonna’s sitting room, they angrily vow to never speak to each other. But not a week later, Josie hits a popular girl in the nose for calling her a slur—and she calls Michael, who’s a barrister (i.e., lawyer), to come get her out of what might become a sticky legal situation. She’s surprised when he comes to her rescue.
Over the next several weeks, as Josie spends afternoons with Nonna, Nonna starts to tell Josie about her young adulthood. She married Nonno in Sicily when she was only 17, and they immigrated to Australia in the 1930s. Nonna was often lonely, since Nonno worked away from home most of the time and no Australian people would teach Nonna English. Things began to change when Nonna met Marcus Sandford, an Australian policeman. He treated Nonna kindly, taught her English, and helped her grow a garden. When Nonno found out about Marcus, he forbade Nonna from seeing him again.
When Josie isn’t with Nonna, she’s working at McDonald’s or fighting with Mama; Mama is casually dating a man named Paul Presilio, whim Josie hates. One night after Josie’s McDonald’s shift, a bully, Greg Sims, assaults her, but Jacob intervenes. They agree to a date the following weekend, but Jacob is upset that Josie wants him to meet Mama. He’s so upset that he purposefully shows up in ratty clothes and is rude to Mama. Enraged, Josie leaves their date within 10 minutes. But as she’s walking home, Michael stops and offers to take Josie for pizza. As they eat, Josie realizes she actually likes Michael, especially when he offers her a job at his law firm photocopying.
As the weeks pass, Josie spends time with her friends and runs into John again—he’s still depressed. She and Jacob also decide to go on another date. They skip school and take the ferry to Manly, where they kiss. Josie knows she’s in love, so it’s difficult to be away from Jacob when Michael takes her to Adelaide for her three-week June vacation. Michael tells Josie the story of how he and Mama grew up together and fell in love.
Not long after Josie gets back, it’s Tomato Day, the day her family gets together to make spaghetti sauce. As they all work, Nonna and Zia Patrizia tell Josie more about Marcus Sandford. During World War II, when Australia interned Italian men—Nonno included—Marcus tried to get Nonno released. When he couldn’t, he continued to help Nonna and Zia Patrizia. Both women moved to Sydney not long after, but Nonna was by herself for four months over Christmas before she could join Nonno in Sydney.
At the end of July, St. Martha’s holds its annual walkathon. Josie, as the school’s vice captain, is supposed to walk at the back of the crowd to keep an eye out for younger students—but Sera, Lee, and Anna convince Josie to skip the walkathon altogether and take a bus to a fancy hotel, where a pop star is supposedly staying. They don’t see the pop star, but they do accidentally end up on TV in the background of a press conference. When the school principal, Sister Louise, scolds Josie for her behavior the next day, she reveals that Josie was actually voted school captain—not vice captain—but Sister Louise didn’t think Josie could handle the responsibility. Josie is upset about this, but also realizes that she’s more popular than she thought.
Josie and Jacob’s relationship is tumultuous: one minute they’re madly in love, and the next they’re yelling at each other. Jacob is upset when Josie goes to see a Macbeth film adaptation with John, and Josie is upset when Jacob tries to pressure her to have sex.
Josie’s world turns upside-down at Mama’s birthday party. As people joke about when Mama was conceived, Josie realizes that Nonno isn’t Mama’s father—Marcus Sandford is, as Mama was conceived during the four months that Nonno was out of town. After the party, Nonna confirms that Josie is correct. After a week of ignoring Nonna, Josie finally asks Nonna about what happened. Nonna explains that Nonno was a cruel husband, while Marcus treated her kindly and gently, and even wanted Nonna to leave Nonno. When Nonna joined Nonno in Sydney and revealed that she was pregnant, Nonno was enraged. He knew she’d conceived Mama with Marcus because Nonno knew he was infertile—something he’d purposefully concealed from Nonna over the course of their marriage. But Nonno agreed to raise Mama as his own, though he resented both her and Nonna. This is why Nonno kicked Mama out when she became pregnant. Nonna swears Josie to secrecy.
The weekend before Josie’s HSC exams, she runs into John at a rugby match and is surprised to find that he’s lighthearted and happy. But the next day, when Josie gets to school, Ivy is sobbing: John committed suicide. Josie spends the next week grieving and feeling angry. She doesn’t think John had a right to kill himself when he had everything—everything Josie wishes she had—though Michael reminds her that wealth isn’t the key to happiness.
A few weeks later, at a school awards ceremony, Josie and Ivy find themselves in the restroom at the same time. Josie realizes they’re not so different—something John tried to tell her the day before he died—and invites Ivy to have coffee once they’re both in college. After the event, Michael takes Josie for pizza. He reveals that he bought a house in Sydney, and that he’d like Josie to take his last name and allow him to adopt her. Josie asks for time to think and later, tells Mama that she might take Michael’s last name, but he doesn’t have to adopt her to be her father.
Not long after, Jacob breaks up with Josie. She sobs for days. But in the aftermath, Josie realizes that she’s become “emancipated” in the last year. Now, she feels at peace with her family history and her Italian identity. She’s ready for the future