After years of pursuing drug kingpin Cullen Crisp, LAPD Detective John Kimble arrests him for murder; a witness saw him murder an informant after getting information regarding the whereabouts of his ex-wife, Rachel Myatt Crisp, who allegedly stole millions of dollars from him before fleeing with his son, Cullen Jr. Partnered with former teacher-turned-detective Phoebe O'Hara, Kimble goes undercover in Astoria, Oregon to find Rachel and offer her immunity in exchange for testifying against Crisp in court. To this end, O'Hara must act as a substitute teacher in Cullen Jr's kindergarten class at Astoria Elementary School. O'Hara gets a terrible case of stomach flu, falling ill at the last moment; Kimble takes her place. The suspicious school principal, Miss Schlowski, is convinced he will not last long before quitting. Overwhelmed at first, he adapts quickly to his new status, despite not having any formal teaching experience. With the use of his pet ferret as a class mascot, positive reinforcement, his police training as a model for structure in class and his experience as a father, he becomes a much admired and cherished figure to the students.