Masumi Mizusawa, a brilliant forensic pathologist returning from the U.S., joins the newly established Medical Examiner Japan (MEJ) alongside inexperienced director Maho Kiryu, and on their first case, they investigate the mysterious death of a 17-year-old boy found in just 40 centimeters of water; as the team conducts their first autopsy, what seems like a simple accident begins to raise troubling questions about whether the death was truly accidental or something more.