The Kairos Files Books in Order

The Kairos Files is a middle-grade supernatural mystery series about kids who find out that the strange things adults dismiss are often very real. Its world includes hidden creatures, supernatural abilities, haunted places, and Kairos, a quiet government agency that investigates the unusual before it becomes a bigger problem.

The series begins with The School for Invisible Boys. Sixth grader Hector Griggs attends St. Lawrence's Catholic School for Boys, where life has become especially hard after his former best friend, Blake, starts bullying him. Hector already feels overlooked, then discovers that he can literally turn invisible. That new ability leads him to Orson Wellington, another invisible boy who has been trapped that way for years.

Something hungry is hiding at the school.

Hector's mystery is not only about escaping a monster. He has to work out who he can trust, face the fear that comes with being singled out, and decide what it means to be seen by other people. Sam Osborne, a mysterious new classmate with her own unusual skills, becomes an important ally as the danger around St. Lawrence's grows.

In A Home for Unusual Monsters, the focus shifts to Sam. She is connected to Kairos and can control how other people perceive her, a talent that makes her useful for undercover work. Still trying to prove that she is ready for more responsibility, Sam is sent to infiltrate the family of a former agent and search for information about monsters living in plain sight. The job is full of secrets, false identities, and clues that do not point where she expects.

The monsters are creepy, but the books keep their feet on the ground.

Across the series, Hutchinson pairs brisk mysteries with problems that feel familiar: loneliness, friendship trouble, family secrets, fitting in, and learning to ask for help. Hector and Sam each bring different strengths to the investigation, and the Kairos agency gives the books an ongoing larger world without requiring readers to know every answer at once.

Expect spooky schools, covert missions, odd powers, and suspense that stays accessible for younger readers. Start with The School for Invisible Boys, then continue with A Home for Unusual Monsters to see Sam take the lead and the hidden world of Kairos open up further.