Miguel is a smart, sixteen-year-old boy with a 3.4 GPA who isolates himself by reading novels. Sentenced to a year at The Lighthouse group home for an unspecified offense, he deals with deep guilt and a belief that he can cause bad things to happen simply by thinking about them. He maintains a required daily journal, which captures his observant, cynical, and highly analytical view of the world and his companions.

Diego is Miguel's older brother, a handsome and popular teenager who easily talks his way out of trouble and attracts beautiful girls. He acts as a mentor figure to Miguel, teaching him how to act cool, but he also possesses a volatile temper that frequently leads to intense physical wrestling matches between the brothers.

Mong is a highly intelligent Asian teenager residing at The Lighthouse. He wears a shaved head and has facial scars, presenting a disturbed, violent exterior that intimidates the other residents. Despite his frightening reputation and unpredictable anger, he is philosophical, highly observant, and wears a mysterious brown tooth necklace for good luck.

Rondell is a large, physically imposing African American teenager who shares a room with Miguel at The Lighthouse. He struggles with reading and takes the Bible literally, finding comfort in religious concepts. He is fundamentally gentle and naive, though he is capable of sudden, extreme physical reactions when pushed.

Mei-li is Mong's beautiful, street-smart cousin. A college student who agrees to transport the boys, she balances a cynical exterior born from relationship troubles with a hidden romantic idealism. She challenges the boys to think about their futures and shares stories about love and maturity.

Flaca is an attractive Mexican girl living in Southern California. She is confident and flirtatious, immediately taking an interest in Miguel and inviting him to a local fraternity party.

Jaden is an optimistic counselor at The Lighthouse group home. With his blonde hair, blue eyes, and tendency to call everyone "bro," he appears slightly out of place among the residents. He genuinely cares about the boys, encourages Miguel to pursue college, and tries to break through their defensive shells.

Les is an older Jamaican man who provides transportation and logistical support for The Lighthouse. He is knowledgeable about the facility's history and tries to lecture new residents on the importance of rehabilitation.

Grandma Castaneda is Miguel and Diego's paternal grandmother. She provides food and shelter when Miguel arrives seeking work. Deeply religious, she prays continuously for her grandsons and tries to offer emotional comfort despite the tension within the family.

Gramps is Miguel's paternal grandfather. He runs a groundskeeping business and communicates almost entirely through demanding physical labor. He maintains a stony silence toward Miguel, focusing strictly on digging trenches and removing trees.