Billy is a 13-year-old boy who lives with his mother and older sister in Florida. He has grown up moving frequently due to his mother's bird-watching habits, making him a loner at school. He possesses a deep fascination with snakes, knowing how to catch, handle, and safely release dangerous reptiles. He is independent and protective, choosing to save his own money to fly to Montana to track down his absentee father.

Summer is a 14-year-old girl of the Crow tribe living in Montana with her mother and stepfather. She is highly responsible for her age, managing Dennis's finances and ensuring the monthly support checks reach Billy's family in Florida. She is practical, courageous, and harbors a deep protective streak for the natural world.

Dennis is Billy and Belinda's absentee father who walked out on the family when Billy was four years old. He has a history of suddenly quitting jobs on Thursdays whenever he feels stifled. Living off an inheritance from his late Aunt Sophie, he uses advanced drones to track and disrupt illegal poachers who target endangered species.

Chrissie is Billy and Belinda's mother, living in Fort Pierce, Florida. She is intensely obsessed with observing bald eagle nesting sites, frequently uprooting her family and moving to different Florida towns just to monitor new nests. She stubbornly blocks her children from contacting their father, insisting he must make the first move.

Baxter is a wealthy trophy hunter from California who specifically targets endangered species. He uses his vast financial resources to bypass regulations and hire locals to set up illegal private hunts. He hunts purely for ego, seeking the thrill of killing rare animals before they disappear from the planet entirely.

Little Thunder-Sky, commonly called Lil, is a middle-aged woman of the Crow tribe who works as a professional catch-and-release trout guide. She met Dennis when his drone crashed into her trailer roof. She is a pragmatic, observant woman who accepts people's eccentricities without judgment and provides a stable home environment.

Belinda is Billy's older sister. Tired of her mother's eagle-chasing relocations, she deeply craves stability and views going away to college as an escape. She is highly focused on social media and her boyfriend, and she maintains a sharp hostility toward the father who abandoned them.

Daisy is Lincoln Chumley Baxter IV's wife. Though she is an expert shot herself, she despises her husband's illegal trophy hunts. She chooses to covertly help Dennis thwart her husband's activities by providing real-time tips on his travel plans and hunting targets.

Axel is a tough-looking Texan who specializes in training Walker hounds to track big cats silently. Despite working in the hunting industry, he adheres to a strict personal code and refuses to participate in poaching endangered animals.

Dawson is Belinda's wealthy prep-school boyfriend. He is a pretentious braggart who invents stories about his family's money and his own sporting prowess. He reveals a cruel streak when he casually attempts to harm a neighbor's pet.

Chin is a smaller, younger student at Billy's school in Florida. After Billy intervenes to stop a bully from attacking him, Chin remains deeply grateful and tries to show his appreciation to Billy.

Rusty is a belligerent ranch hand with distinctive red hair who works on a fenced property in Florida. He uses his position to secretly facilitate illegal hunts on the ranch for wealthy poachers.

Limpy is a local Florida surfer who serves as a hired courier. He knows nothing about drone technology and is easily pressured into revealing information about the person who paid him to run the errand.