Gratuity is an independent eleven-year-old biracial girl recounting her journey during the Boov occupation. After extraterrestrials abduct her mother, she relies on her resourcefulness to survive alone. She learns to drive her mother's car and takes a cross-country trip toward Florida with her cat. She displays courage and clear morals when dealing with hostile forces.

J.Lo is a Boov with greyish-blue skin and tiny arms who takes on a human-sounding name. He modifies Gratuity's car into a hovercraft to secure a ride to the Human Preserve. As a mechanic who accidentally alerted hostile extraterrestrials to Earth's location, he hides from the Boovcops. He initially views humans as inferior animals but begins to change his mind as he travels.

Lucy is Gratuity's mother. The Boov abduct her to serve as a language tutor due to her bilingualism. When the human population faces displacement in Arizona, she steps into an unexpected community leadership role. She attempts to help displaced families while working alongside questionable human leaders.

Pig is an indoor cat who stays with Gratuity during the Great Housecat Betrayal, an event where most felines abandon humans for the Boov. Pig provides Gratuity with a sense of normalcy and family during the invasion. Her natural feline traits unexpectedly influence their encounters with other species.

Daniel is a wealthy, opportunistic man who assumes a leadership position on an Arizona reservation. He relies on his material possessions to project intelligence and authority. He prioritizes secret deals with extraterrestrial invaders over the safety of the human population.

Frank is a 93-year-old Diné man living in Roswell. He claims to have found an alien pod in 1947, a story local residents dismiss. He maintains a junkyard filled with machinery and puts on an erratic public act to protect his property. He ignores the mockery of his white neighbors and quickly assesses the true nature of Gratuity's alien companion.

Vicki is a lifelong Roswell resident and avid conspiracy theorist. She holds romanticized ideals about alien invasions that clash with the harsh reality of the Boov occupation. She acts overbearingly protective of Gratuity while harboring intense prejudice against Frank.

Christian is a friendly boy surviving in the abandoned theme park tunnels. Like Gratuity, he lost a parent to the Christmas Eve abductions. He guides Gratuity and helps her escape from hostile Boov patrols.

Curly is an older boy surviving in the Florida Human Preserve. He exhibits hostility toward outsiders and distrusts Gratuity, especially after her alien companion arrives.

Kat is a suspicious Roswell resident trapped in the town after the invasion. She questions Gratuity's story and immediately suspects JayJay might be a Boov in disguise.

Mitch is a government worker who informs Gratuity about Daniel Landry's negotiations. He represents the human officials who comply with the invaders rather than resisting them.

Katherine is a woman in the Tucson community who claims to be a friend of Lucy Tucci. She attempts to show Gratuity around but meets resistance from the cautious young girl.

Captain Smek is the authoritative leader of the Boov forces occupying Earth. He enforces the relocation of humans and spreads propaganda about the Boov's manifest destiny to colonize the planet.

Trey is a rude and highly skeptical resident of Roswell. Despite his abrasive demeanor, he steps in to help Frank after a violent encounter with an alien machine.