Charlie is the thirteen-year-old narrator of the story. Unconventionally homeschooled and socially isolated by his father, he possesses a quiet empathy and an observant nature. He acts as his father's captive audience and feels conflicting emotions of admiration and embarrassment regarding his family's eccentric lifestyle. He is acutely aware of how different he is from his peers but often stays silent to avoid confrontation.

Allie is a brilliant but paranoid inventor who holds nine patents. He holds deep-seated cynicism toward the United States government and modern consumer culture, firmly believing a catastrophic war is imminent. Narcissistic and highly critical, he constantly demands an audience and belittles anyone who disagrees with him. He decides to move his family to the jungles of Honduras to establish a self-sustaining settlement under his absolute control.

Mother is a compliant and optimistic woman who completely defers to her husband's authority. She accepts the rules Allie sets and willingly remains uninformed about major decisions regarding the family's future. While she shows consistent tenderness toward her children, her absolute loyalty to Allie prevents her from intervening when his behavior becomes erratic or unreasonable.

Jerry is the eleven-year-old middle son of the Fox family. Conditioned by his father to compete with his older brother, he initially embraces opportunities to mock Charlie. He is less resilient than his brother and prone to complaining when physically taxed. He serves as an early indicator of dissent within the family structure as they adjust to their new environment.

April is one of the five-year-old twin daughters in the Fox family. She is eager to please and easily absorbs her father's worldview. She actively echoes his statements and seeks out his praise, serving as an eager disciple of his unconventional philosophies.

Clover is the five-year-old twin sister of April. Like her sister, she fully accepts her father's authority and repeats his doctrines. She possesses a naturally assertive and bossy streak, confidently issuing orders to adults and children alike despite her young age.

Tiny Polski is the owner of a farm in Hatfield, Massachusetts, and Allie's initial employer. He recognizes Allie's engineering talent but quickly loses patience with his insubordinate, insulting attitude. He demonstrates concern for Charlie's well-being, recognizing the potential danger Allie poses to his family.

Captain Smalls commands the cargo vessel that transports the Foxes to Honduras. He is initially cordial and practical, attempting to warn Allie about the harsh realities of the jungle. He shows kindness to Charlie by inviting him to the bridge, which draws Allie's competitive ire.

Reverend Spellgood is a prominent evangelical preacher returning to his mission in Guampu, Honduras. He frequently quotes scripture and represents the organized religion that Allie aggressively despises, sparking immediate ideological tension between the two men.

Emily is the daughter of Reverend Spellgood and is close in age to Charlie. She chatters incessantly about her family's comfortable lifestyle, television shows, and pop culture. Her worldly knowledge highlights Charlie's deep social isolation, though she is just as influenced by her father's worldview as Charlie is by his.

Mr. Haddy is the operator of The Little Haddy, a boat he uses to ferry passengers and cargo along the Honduran coast. The boat is his sole livelihood and most prized possession. He attempts to guide Allie safely through the riverways but is consistently overruled by Allie's stubborn demands.

Mr. Weerwilly is a German immigrant who originally attempted to establish a banana farm at the Jeronimo settlement. He eagerly sells the remote, overgrown property to Allie, openly expressing his relief to be rid of the challenging location.

Mr. Maywit is an Indigenous Honduran man who lives with his family at the Jeronimo site. He is deeply religious and remarkably humble, consistently deferring to Allie's demands and accepting his patronizing attitude without complaint in exchange for remaining on the land.

Francis is an Afro-Miskito man who lives in a settlement near Jeronimo. He works alongside Allie to clear vegetation, build structures, and transport heavy loads, enduring Allie's relentless demands and harsh physical expectations.

John is a Zambu resident of the surrounding area who contributes his labor to Allie's ambitious construction projects. He assists in the grueling task of dragging massive blocks of ice through the jungle.

Bucky is a local Zambu resident who helps the Fox family transition into the jungle. He is part of the small crew enlisted by Allie to perform the exhausting physical labor required to transport ice overland to remote villages.

Mr. Struss is a missionary operating in the region who visits the Jeronimo settlement to check on the local inhabitants. He is met with intense hostility from Allie, who claims private ownership of the land and immediately attempts to banish him.