Matthew is a ten-and-a-half-year-old boy who loves adventure stories and leads a neighborhood adventure club. Though initially impulsive and prone to ignoring the consequences of his actions, he demonstrates genuine care for his friends. When experiencing the harsh realities of the Revolutionary War firsthand, he struggles to adapt but slowly learns the true meaning of leadership and responsibility.

Katie is Matthew's spunky, seven-year-old sister who secures an invitation to the campout by threatening to tell their parents about the hidden peas. Armed with toy weapons, she eagerly joins the adventure but often acts her age, voices complaints, and wanders into unsafe situations. Her bold nature inadvertently initiates the group's journey through time.

General Washington is the Commander of the Continental Army, leading his bedraggled troops through a freezing winter storm toward Trenton. He projects strength, patience, and authority, inspiring deep devotion from his men despite their terrible conditions. His leadership style and surprising moments of personal kindness provide Matthew with a concrete model of responsibility under intense pressure.

Brian, almost exclusively called Hooter by his friends, is physically larger and stronger than the other club members. He acts as the group's strong man, though his imposing size contrasts with his deeply sensitive and empathetic nature. He famously cared for a baby owl in the past and consistently advocates for kindness, readily showing compassion toward individuals others view as enemies.

Q is an intelligent, intellectually curious student who acts as the brain and strategist of the adventure club. He quickly assesses their historical surroundings and relies on his knowledge of history and astronomy to make sense of their situation. He places high value on historical artifacts and reveres figures from the American Revolution.

Tony is the smallest member of the adventure club, a physical trait that earns him the role of the group's scout. He tends to follow the rules and worries about getting into trouble, providing a cautious voice against Matthew's impulsive plans. He shares vital local lore from his grandfather regarding mysterious disappearances at the lake.

Israel is a young, impoverished soldier in the Continental Army who enlisted as a paid substitute to provide food and money for his younger siblings. Shoeless and suffering from a severe infection, he struggles to endure the brutal winter march toward Trenton. He acts as a mentor and ally to Matthew, offering guidance, sharing his meager provisions, and providing a sobering perspective on the harsh realities of army life.

Gustav is a young Hessian soldier hired to fight for the British against the Continental Army. Despite his imposing appearance and role as an enemy combatant, he demonstrates surprising humanity and compassion toward the children. His respectful, gentle demeanor and brave actions challenge the boys' preconceived notions about their historical enemies.

Mr. Carlton is Matthew and Katie's father. He maintains household rules and encourages patience, an attribute Matthew recalls when observing General Washington. He praises Matthew for taking responsible care of his younger sister during the campout.

Mrs. Carlton is Matthew and Katie's mother. She worries about the children's proximity to the lake and provides the daily comforts of home that Matthew deeply misses during his historical ordeal.

Adam is a young corporal in the Continental Army and the grandson of a man who previously disappeared on Lake Levart. He receives orders directly from an officer to transport the strange children across the river to safety.

Captain McCowly is a harsh, rum-scented officer in the Continental Army. He strictly enforces orders and refuses to listen to Matthew's explanations, violently pushing the young boy into the marching column heading for Trenton.

Nathan Hornbee is an older farmer who sympathizes with the rebel cause but avoids actively fighting to protect his farm and livelihood. He provides Matthew with vital shelter, warm food, dry clothing, and a mule during a desperate moment in the wilderness.

Temperance is Nathan's wife, a woman deeply anxious about their local Tory neighbors and the ongoing war. Her fear of the conflict manifests as a harsh and bitter demeanor, causing her to demand Matthew leave their property, though she ultimately shows a small moment of practical sympathy.

Henry is a drummer for the Continental Army, wearing a red uniform so officers can easily locate him to communicate orders during battle. He provides a blunt, pragmatic view of wartime survival and attempts to force Matthew to abandon his sick friend for his own safety.

Corporal Neeley is a Continental Army soldier assigned to help escort the displaced children toward the safety of McConkey's Inn away from the front lines.

Abigail is Israel's younger sister back home in Massachusetts. Her existence motivates Israel to survive his enlistment, as he plans to bring her a gift of blue glass beads.