Arson investigator Samantha Orland calls upon the Special Crimes Unit for help with a case that gets escalated to attempted murder when a serial arsonist's most recent fire involves a family. Although all evidence points to a local fire artist, Backstrom is positive their arsonist is someone they least suspect. The investigation takes a turn when the team discovers evidence missing from the crime scene and Backstrom suspects someone insides the investigation. Meanwhile, Backstrom gets tormented by childhood neighbors who stole something very special from him when he was younger and Valentine helps Niedermayer recover stolen evidence.