Cally is a fifth-grade student struggling with grief following her mother's death a year prior. She often feels ignored or misunderstood by her family, teachers, and peers, leading her to initiate a sponsored silence that she chooses to continue indefinitely. She loves music and possesses a deep capacity for empathy.

Cally and Luke's father is weighed down by depression and financial stress following the death of his wife. He works at a warehouse that is downsizing and struggles to support his family financially and emotionally. He handles his grief by avoiding the topic entirely, shutting down any conversation about his late wife and isolating himself from his children.

Homeless is a massive silver-gray Irish Wolfhound who forms an immediate bond with Cally. He is loyal, gentle, and protective, standing as high as Cally's waist. Despite his size intimidating some adults, he offers unconditional love and a comforting presence to those who treat him with kindness.

Cally and Luke's mother died in a car accident exactly one year before the story begins. Though she is no longer living, she appears to Cally as an apparition in a red raincoat during moments of distress or confusion. Before her death, she loved singing and filled the family's home with warmth, baking, and music.

Luke is Cally's 13-year-old older brother. He spends most of his time playing video games in his room and often seeks peace and quiet away from family stress. Though he initially appreciates Cally's silence, he soon notices the deeper issues affecting their family and openly expresses his anger toward their father's decisions.

Jed is a quiet, kind man experiencing homelessness in Cally's town. He wears a purple puffy jacket and split sneakers. Despite facing harassment from local boys and suspicion from adults like Cally's father, he maintains a gentle demeanor and takes careful care of his canine companion.

Sam is a boy around Cally's age who lives in the apartment directly below the Fishers' new unit. He is blind, mostly deaf, and has a heart murmur along with asthma. Highly independent, he communicates through a deafblind alphabet tapped onto skin and resists his mother's attempts to coddle him. He dreams of learning how to swim.

Mrs. Cooper is the barefoot, friendly woman living downstairs from the Fishers. She works tirelessly to make her apartment safe and accessible for her son, Sam, padding furniture corners and using a drum instead of a doorbell. She is generous with her time and food, continually extending kindness to Cally's family and people in need.

Mia is Cally's former best friend at school. She distances herself from Cally following Cally's mother's death and her subsequent behavioral changes, choosing instead to spend time and perform with another classmate.

Daisy is a classmate of Cally who replaced her in the lead role of the school musical the previous year. She often teases Cally and monopolizes Mia's friendship.

Miss Steadman is Cally's fifth-grade teacher. She announces the sponsored silence fundraiser for a children's hospice charity and frequently reprimands Cally for daydreaming or failing to pay attention in class.

Mr. Crisp is the school music teacher who recognizes Cally's singing talent. He remembers her mother fondly and encourages Cally to participate in school performances despite her ongoing silence.

Mrs. Brooks is a teacher assigned to help students with behavioral issues or disabilities. She notes changes in Cally's behavior since third grade and tries to intervene when Cally's silence begins affecting her academic participation.

Dr. Colborn is a small woman with short grayish hair and freckles who is brought in to evaluate Cally's silence. She prefers to form her own opinions rather than rely on the school's reports and approaches Cally with patience and respect.

Rachel is an energetic friend of Luke who brings a lively atmosphere to the Fishers' home. She enjoys painting faces, cooking, and making music.