Brewster is a sixteen-year-old high school student who intentionally isolates himself from his peers. He lives in a rundown house with his bitter uncle and younger brother, hiding his intelligence and love for poetry behind a rough exterior. He secretly possesses a supernatural ability to absorb the physical and emotional pain of anyone he cares about, leaving his body covered in unexplained scars and bruises.

Tennyson is a sixteen-year-old lacrosse player who aggressively protects his twin sister, Brontë. He has a quick temper and a tendency to intimidate others when he feels challenged. He prefers to ignore the growing tension in his parents' marriage by focusing on his athletic and social life, rarely looking below the surface of his daily interactions.

Brontë is Tennyson's sixteen-year-old twin sister, an independent and friendly student who works as a library assistant. She refuses to judge others by high school rumors and intentionally seeks out Brewster to draw him out of his shell. She tends to wear emotional blinders, focusing on positive projects to avoid confronting her parents' failing marriage.

Cody is Brewster's eight-year-old younger brother who relies entirely on Brewster's protection. Because Brewster magically absorbs all of his physical and emotional pain, Cody acts recklessly. He frequently jumps off roofs or antagonizes his angry uncle without fearing the consequences, lacking an understanding of how his actions physically impact his older brother.

Hoyt is Brewster and Cody's alcoholic uncle and legal guardian. He works a construction job where most of his wages are garnished for child support from a previous marriage. He recognizes that Brewster absorbs physical injuries, allowing him to inflict abuse on the young boys without leaving marks on Cody.

Mr. Sternberger is Tennyson and Brontë's father, whose marriage is quietly failing after he committed infidelity in the past. He avoids confrontation in his home, opting to order takeout rather than cook for his family. As his relationship deteriorates, he emotionally withdraws and moves into the guest bedroom.

Mrs. Sternberger is Tennyson and Brontë's mother, who struggles with the fallout of her husband's past infidelity. She has grown emotionally numb and distances herself from family dinners. She secretly begins seeing another man, lying to her family by claiming she is taking Monday night classes.

Katrina is Tennyson's high school girlfriend. They originally wanted to date each other's friends but settled for one another when those plans failed. She dislikes miniature golf but tags along with Tennyson's schemes, eventually growing distant as his focus shifts.

Ozzy is a popular high school swimmer who frequently bullies Brewster. He acts aggressively and feels entitled to his social standing, quickly resorting to physical confrontation when challenged by Tennyson or Brewster in the cafeteria.

Dr. Thorlock is the man Mrs. Sternberger secretly dates while claiming to be at a Monday night class. He eventually visits the Sternberger family home, bringing the parents' unspoken marital conflict out into the open.

Amanda is a high school classmate of Brontë's. She previously ignored Brewster but suddenly shows interest in him once he makes the local news for a heroic act, eventually inviting him to her sixteenth birthday party.

Joe is a student at the high school who previously mistreated Brewster. He jumps on the social bandwagon to befriend him after Brewster's rescue of Cody makes the local news, offering a public apology in the cafeteria.