Emerson is a 12-year-old boy classified as a level five RISK due to his uncontrollable ability to float. He must constantly wear a heavy weighted vest and iron shoes to prevent himself from floating away into the sky. Having lived an extremely sheltered life mostly confined to his bedroom playing video games, he is initially timid, socially isolated, and terrified of heights.

Murphy is a 12-year-old time traveler who frequently and involuntarily vanishes to visit different eras. His family struggles financially, and he attends the camp under strict surveillance from the Time Travel Bureau of Investigation. Because he has seen his own funeral in the future, he approaches the summer believing he will soon die, approaching his final months with a mixture of fear and a desire to experience life fully.

Hank is an outgoing 12-year-old camper who turns invisible involuntarily, though his clothing remains fully visible. He serves as an adventurous foil to the more cautious boys in his cabin, frequently removing his clothes to sneak around undetected. He maintains a running "life list" of goals and refuses to let fear dictate his summer.

Eli is the counselor in his early twenties responsible for the Red Maple cabin. His RISK factor causes his body parts to change shape or size without warning, sometimes leaving him with arms half their normal length. He balances his official responsibility to keep the campers safe with a quiet appreciation for their rebellious independence.

Gary is a camper whose hands involuntarily stick to surfaces, requiring painful caustic acid treatments for removal. Diagnosed with ADHD and ODD, he harbors deep frustration over how his family and society treat him. He initially pushes his peers away and acts with hostility, believing his abilities make him nothing more than a dangerous burden.

Anthony is a camper in the Red Maple cabin who suffers from spontaneous combustion. Parts of his body catch fire without warning, requiring him to wear flame-resistant clothing at all times and exercise extreme caution when standing near his fellow campers.

Zeke is a short camper whose uncontrollable X-ray vision frequently overrides his normal sight, essentially blinding him to regular surroundings. He relies heavily on his trained service skunk to alert him before his vision shifts so he can find a safe place to sit down.

Molly is a 12-year-old girl in the Monarch cabin who involuntarily transforms into a spaniel. She catches Emerson's attention early on, proving to be approachable and friendly, which helps Emerson build the confidence to speak with her.

Kirsty is a camper in the Monarch cabin whose skin is constantly burning hot to the touch. She responds favorably to Hank's theatrical, Shakespeare-quoting flirting methods, even giving him a hair ribbon.

Emerson's mother is a highly nervous woman who lives in constant terror that her son will float away and die. Her trauma regarding his safety has led her to enforce an extremely sheltered lifestyle for Emerson, relying heavily on weighted gear to keep him grounded indoors.

Mr. Blue is the leader and director of Camp Outlier. Named for his blue skin, he strives to create an inclusive, safe environment where children with RISK factors can experience a normal summer without societal prejudice or fear.

Mr. Stink is a trained service skunk who assists Zeke with his visual impairment. The animal reliably sneezes or alerts Zeke immediately before his X-ray vision activates, keeping the boy safe from sudden bouts of blindness.