Ben is a determined middle schooler living in a small town with an annual lantern-releasing tradition. He commits to a strict pact with his friends to follow the floating lights downriver until they discover their final destination. Prone to pessimism and rigid in his ways, he struggles to adapt when his peers abandon the quest and leave him to travel into unknown territory.

Nathaniel is a clever, optimistic middle schooler whose eccentric interests make him a target for bullying at school. Despite being actively shunned by Ben's friends, he trails their expedition out of a desire to spend time with Ben. He possesses a deep fascination with astronomy and maintains a cheerful disposition in the face of rejection.

The Fisherbear is an anthropomorphic bear participating in his own cultural tradition regarding the autumn equinox. He carries an old family map and searches for a specific fishing spot, believing the town's paper lanterns are actually fish. He acts as an unexpected guide for the boys, offering them stories, advice, and practical help.

Madam Majestic is a tiny, elderly potion-maker who lives in a cave high on a cliff face above the lake. She busily prepares for the arrival of mysterious guests, brewing magical mixtures to alter the moonlight. She operates as a demanding and eccentric figure who requires strict payment for her magical services.

Mikey is a middle schooler and one of Ben's original companions on the lantern-following quest. He abandons the pact early in the journey because he does not want to miss his family's taco night. He participates in the group's mockery of Nathaniel before turning back.

Elliot is part of Ben's friend group and originally agrees to the pact to follow the paper lanterns. Shortly after Mikey leaves, Elliot silently drops out of the expedition, turning his bike around and heading home without offering any explanation.

Adam is one of the five boys who initially swear not to look back or turn for home. He abandons the quest when the group reaches Toad Canyon Bridge, retreating because he fears parental punishment if he crosses the forbidden boundary.

Sammy is a member of Ben's original bicycle expedition. Like Adam, his fear of getting into trouble outweighs his curiosity, and he refuses to cross Toad Canyon Bridge, choosing instead to break the pact and return home.

Sebastian is a large white dog belonging to Madam Majestic. He assists his owner in herding the boys into the cellar and possesses magical qualities, including the ability to run rapidly across the surface of the water.

Margaret is an enormous, highly trained crow kept by Madam Majestic. When given special magical eye drops, she serves as an avian cartographer, flying over the region and returning to draw highly detailed maps with a pot of ink and her beak.