Wong Yun writes to Meng using what she calls a “Reforged pencil,” stating that her words are being transmitted directly to Meng. She wants to ask for forgiveness and explain how she perceives their shared history.

In 1937, 10-year-old Meng and her mother arrive at the Phoenix Pencil Company in Shanghai, fleeing the war. At their first dinner together, Yun and Meng fight over a tofu puff. The cousins are jealous of each other while remaining oblivious to the Japanese invasion happening around them.

At school, Yun bullies Meng, who doesn’t speak the local dialect, by drawing a cruel caricature and showing it to their classmates. Meng confronts Yun afterward and borrows her pencil. That night, Yun’s mother shows Yun an altered version of her drawing in which the original lines look dark and dripping as if they’ve been retraced with a calligraphy brush. She threatens to disown Yun if she makes more caricatures of her cousin. When Meng returns Yun’s pencil to her, it’s missing its graphite heart.

As punishment for bullying Meng, Yun’s mother makes her hold a chair above her head every night for a month while Meng watches. During this time, they begin bonding. Each cousin idolizes the other’s mother: Yun admires Meng’s mother’s social grace, while Meng observes Yun’s mother’s skill at crafting pencils.

Yun overhears their mothers arguing about a family power. When she presses Meng, Meng shows her the long, thin scars on her forearm. Yun recognizes them from a buried memory of her own mother’s arm.

Yun writes that she has kept the secret of the pencils from Monica. She reveals she recently received a diagnosis that will cause her to lose her memories and is writing to preserve them before they disappear.

On August 18, 2018, Monica arrives at a Boston bus station, where her grandparents are waiting. Seeing them, she begins crying. On the train home, her grandfather cheers her up by asking about a coding technique.

At home, Monica gives her grandmother the pencil from Meng. Her grandmother reacts with little emotion but insists it means everything to her. At dinner, Monica suggests going to Arby’s for her grandmother’s birthday per tradition, but her grandmother declines, citing health concerns.

That night, her grandfather tells Monica that her grandmother was diagnosed with memory loss over the summer. They didn’t tell Monica earlier because they knew she would abandon her studies to return home. Her grandmother’s real reason for declining the restaurant visit is that she becomes anxious when far from home. Monica’s grandfather also explains that she’s trying to write something for Meng before she forgets.

Monica feels overwhelmed with guilt for being unaware of her grandparents’ suffering all summer. She texts Louise that her grandmother has Alzheimer’s, and Louise responds immediately with sympathy.

Wong Yun writes that Monica has returned home and that she and her husband have prepared all her favorite foods. She reflects on her son Edward’s estrangement from Monica’s grandfather, Torou, before writing about her childhood.

In 1939, Yun’s father, a former doctor and spy named Kangshen, returns home after escaping from Japanese-occupied territory. He has Yun deliver a letter hidden inside a box of custom pencils to a man named Mr. Gao in the French Concession, with instructions to tell him to send his reply using a pencil.

Mr. Gao gives Yun one of the family’s own pencils as his response rather than a written letter. Believing it contains a hidden message, Yun conceals it and lies to her mother, claiming Mr. Gao had sent nothing besides payment.

The next day, Yun confronts her aunt about the pencil. Her aunt takes it and reveals that Yun’s grandmother has forbidden them from telling Yun anything in an effort to keep her safe. When Yun asks to see her aunt’s arm, she rolls up her sleeve just enough to reveal a scar shaped like a phoenix’s head.

A few days later, after receiving the message from the pencil, Kangshen leaves on another dangerous mission. To cheer up her daughter, Yun’s mother gives her one of her father’s old, worn-down pencils. She explains he used it to write love letters to her and tells her cryptically that she’ll find those letters herself one day.

When Monica was eight, her father moved to Shanghai. Her only way to communicate with him was by email, and her grandfather helped her send her first message, which sparked her love for technology. Over time, her correspondence with her father dwindled.

In the present, Monica emails her father about her grandmother’s illness and decides she must take the semester off to care for her grandparents. When she tells her grandmother, Yun is upset and argues against it. Monica asks about the happiest days of her life, and her grandmother says it was raising Monica. Her grandmother then notices how often Monica checks her phone for messages from Louise and asks if she has a boyfriend.

Suddenly, her grandmother becomes disoriented. She opens a pot on the stove, freezes as steam erupts around her hand, and drops the lid. Monica rushes her to the sink and runs cold water on the burned hand. When Monica’s grandfather arrives, her grandmother rubs her wrist and asks for a pencil, believing they are in danger. He calms her, reminding her they’re safe in America, and her confusion passes. Monica tells her grandfather she’s staying home for the semester. He accepts without protesting, confirming how much they need help.

Monica texts Louise her decision. When Louise gently suggests Monica isn’t letting herself process her situation emotionally, Monica feels angry and doesn’t reply. The next morning, she bikes to a distant Arby’s to clear her head and then calls Louise and apologizes. Louise proposes an experiment: Each day, they’ll share one happy and one sad thing with each other. Monica agrees.

Monica brings home Arby’s sandwiches, and she and her grandparents celebrate Yun’s birthday. On a bench by the river, her grandmother tells Monica she wants to teach her about the pencils before she forgets.

That night, Monica texts Louise her highlights. Louise replies that talking to Monica was one of her happy moments. Feeling a rush of emotion, Monica asks for Louise’s address so she can send her something.

In a message to Meng, Wong Yun writes that she’s losing her memories and fears forgetting her family. She reflects that she now understands why her grandmother tried to protect her by keeping the secret of the pencils from her.

Yun continues to relate the story of her childhood. As World War II escalates, business at the pencil company slows, and the International Settlement grows crowded with refugees. One rainy night, a distressed woman arrives and asks for Yun’s mother while the girls’ mothers are out. The woman’s husband, a colleague of Kangshen’s in the intelligence division, has been caught and killed by the Japanese. She begs them to use their power on his old pencils so she and her son can preserve his poems. Yun’s grandmother refuses, but Meng steps forward and says she can do it. While Meng works in the back, Yun feels intense jealousy at being excluded from the family’s power. Meng returns with a bandaged arm and gives the woman a notebook filled with her late husband’s poems.

When their mothers return home, Yun’s grandmother has a change of heart. Fearing for her only son’s life, she orders Yun’s mother to teach Yun the power so Yun can know her father even if he doesn’t return from the war. As Yun helps her grandmother to her room, the woman tells her to use the power to survive.

In the present, Yun reflects that, while the power has caused pain, it’s also connected people through their stories. She decides Monica should learn it so she’ll know she’s not alone.

Monica notes that her grandmother’s memory is worsening. For example, she prepares a second batch of meatballs, having forgotten the first. Monica gets permission to send the extras to Louise.

Her grandmother begins teaching Monica about the Phoenix pencils, demonstrating how they are superior to standard pencils because they don’t shatter when dropped, the wood is precisely angled, and the graphite heart is perfectly balanced. Monica finds the technical details uninteresting but accepts a Phoenix pencil to use for a few days. She draws a card with it to send along with the meatballs. The next day, Professor Logan calls and offers her a paid, remote position to continue working on EMBRS. Monica accepts enthusiastically.

That night, she sends Louise her daily summary. As they exchange messages, Monica notices a pattern: Louise deflects personal questions and shares less about herself than Monica does. When Monica asks about the new major Louise is considering, Louise gives a vague answer.

Inspired by the concept of sharing openly, Monica texts Louise that she really enjoys talking to her. In her diary, Monica admits she spends most of her time thinking about Louise. Confused, Monica grabs the Phoenix pencil and draws a tangle of abstract lines with a caption asking how Louise can make her feel this way. She tears up the drawing and takes it to the kitchen to throw away. Upon returning to her room, she finds a response from Louise and begins drawing another tangle of lines.