In April, 35 men and six women enter the prefectural police academy as its 98th class of recruits. Six linked episodes follow the class as it moves toward graduation day half a year later, with some of the recruits surmounting the challenges and proceeding ahead, and others, overcome by the trials, falling by the wayside.
As new hires, students of the academy have already joined the world of work, but unless they can successfully complete the academy course, they will not ultimately become working police officers. Those unable to meet the challenge will be culled; the resulting tension provides crucial backbone to the mysteries at the heart of each tale.
The protagonist of the first story is a former grade-school teacher named Miyasaka. His desire to make a career change was prompted by an experience he had on a ski trip while in college, when he nearly froze to death following a car crash but a policeman named Hirata came to his rescue in the nick of time. As it happens, Hirata's son Kazumichi is among his fellow recruits in the 98th class. Because of the debt of gratitude he owes Hirata, Miyasaka tries to cover for Kazumichi's poor performance a number of times, but his efforts only seem to distress Kazumichi, who mixes some bath salts containing sulphur with some acidic cleanser and attempts a suicide in which he will take Miyasaka with him.
Enter instructor Kazama, who divines what Kazumichi is up to and manages to prevent the tragedy?in part because he senses something odd with Miyasaka during a training exercise on how to question a suspicious individual encountered on the beat. Kazama is in fact the overarching protagonist of the book as a whole?the "detective" who solves the mysteries encountered in each episode. He keeps a sharp eye on the relationships among the recruits as they go through their grueling training, at times questioning their motivations for wanting to become a police officer, at times exploding in anger, and at times offering valuable advice.
Clues rooted in the workaday details of the police officer's career for which the recruits are being trained?from how to handle a sidearm or drive a police cruiser to making a traffic stop or helping someone who's been injured?add touches of realism to the resolution of the mysteries.