Dan is an eleven-year-old orphan with a highly mathematical mind. He channels his energy into collecting physical items like baseball cards, rare coins, and casts. Beneath his energetic exterior, he misses his deceased parents deeply and keeps a single photograph of them hidden in his backpack. He joins his sister on a global clue hunt to honor his grandmother's final wishes.

A fourteen-year-old orphan, Amy is deeply knowledgeable about history and culture. She experiences heavy social anxiety and frequently freezes up or stutters during stressful confrontations. She relies on her younger brother to speak for them in tense moments, but uses her exceptional research skills in libraries to decipher the historical clues left by her grandmother.

Grace is the recently deceased matriarch of the powerful Cahill family. A former world-traveling cartographer, she kept the true nature of her family's historical influence a secret from her grandchildren. She leaves behind a challenge that forces her descendants to choose between a guaranteed inheritance of one million dollars or a dangerous global quest for hidden power.

McIntyre serves as Grace Cahill's trusted estate lawyer and executor. He administers the mysterious clue hunt to the assembled relatives and outlines the rules of the competition. While he occasionally offers subtle assistance to Amy and Dan, his private meetings with a mysterious man in a dark suit make his true motives ambiguous.

Nellie is a college student hired to work as an au pair for Amy and Dan. She speaks French and Spanish fluently, presenting a generally aloof demeanor marked by dyed hair and a nose ring. She agrees to chaperone the siblings on their trip and quickly becomes fiercely protective of them against their hostile relatives.

Ian and Natalie Kabra are glamorous teenage siblings representing the Lucian branch of the family. They use extensive financial resources, private jets, and sophisticated weaponry like poison darts to track the clues. Their calculating cruelty inspires fear in both the children and the adult competitors.

Beatrice is the wealthy, miserly guardian of Amy and Dan following the death of their parents. She parks the siblings in a small apartment under the supervision of hired caregivers, showing little personal interest in their well-being. She is aggressively opposed to the clue hunt and threatens to send the children to foster care for participating.

The Holts are a muscular offshoot of the Cahill family who operate like a militant brigade. Eisenhower, Mary-Todd, Hamilton, Reagan, and Madison wear matching purple tracksuits and employ brute physical strength over intellectual strategy. Their aggressive tactics make them a persistent physical threat to the other competitors.

Ned, Ted, and Sinead Starling are triplet siblings participating in the family competition. They maintain an elitist attitude and refuse to collaborate with the younger children. Their dismissive nature leads them directly into a dangerous trap early in the competition.

Jonah Wizard is a famous teenage reality television star competing in the challenge alongside his businessman father. He affects an artificial street persona for the cameras and uses his vast wealth to bypass obstacles. He enters the competition to secure even greater fame and cultural dominance.

Alistair is a Korean member of the Cahill family who claims to have invented the microwavable burrito. He operates independently in the competition and frequently proposes alliances with other teams, only to double-cross them when an opportunity arises. He relies on deception rather than direct confrontation.

Irina is a former KGB agent participating independently in the clue hunt. She prefers to work alone. She uses espionage tactics, tracking devices, and poison-tipped fingernails to neutralize her competition, holding a deep disdain for the softer members of her family.

Saladin is an Egyptian Mau cat who previously belonged to Grace Cahill. He requires a specialized diet of red snapper and provides a living emotional connection to Grace for her grandchildren. He accompanies Amy and Dan during the initial stages of their journey before being left in safer hands.