After a bad batch of drugs claims the lives of two brothers, the race is on for the squad to find the dealer before more of their fellow high school students are threatened. Feeling smothered by his new around-the-clock security detail, Rusty faces a big decision.

When a newly released prisoner misses two back-to-back parole meetings, the squad is called in to track him down after the suspect’s therapist expresses concerns over his mental state. Meanwhile, Sharon invites therapist Dr. Joe Bowman to the office to evaluate Rusty over a game of chess.

When a body turns up at a posh country club in a quiet neighborhood, the squad’s investigation leads them down a money trail full of surprises. Flynn is noticeably distracted on the job, and Emma’s actions have Rusty questioning her intentions, causing him to distrust her even more.

Christmas vacation is interrupted for the Major Crimes Division when a baseball scout is found dead in his RV. The squad works through the murder case, unfolding a complicated kidnapping scheme. Meanwhile, Rusty opens up to Dr. Joe about his mom.

When a well-off graduate student gets shot to death in a gang-riddled neighborhood, the Major Crimes Division must work with the FBI, including Fritz Howard, to find his killer. Throughout the investigation, it is revealed how each member of the unit became interested in joining the police force.

The squad must work quickly to track down a serial killer before he strikes again. Meanwhile, things get dangerous over a game of chess.