Detective Charlie Hudson teams up with what he calls his "highly trained law enforcement animal" German Shepherd dog named Rex who he prefers to team up with because he doesn't talk his ear off.
After a raw diamond is found at the crime scene of a murder, Major Crimes sets up a stakeout to take down the suspected gem smugglers, but an undisclosed team connection threatens to derail the investigation.
Charlie, Rex, and Sarah travel to an isolated island community caught up in a resettlement dispute. Donovan tries to stop a British police officer from derailing the investigation.
After the owner of a construction company is found dead, Charlie and Rex track the killer to an underground casino. Major Crimes goes undercover to solve the case.
When Officer Power and her K9 partner Rebel are violently attacked responding to a call about a warehouse break-in, Major Crimes is at the ready, but their hearts are heavy as the case hits close to home.
A Jamaican ex-pat who owns a seafood export company is murdered. Charlie and Rex discover a recently fired employee may hold the key to finding her killer.
Rex is suspended after a medically retired officer accuses him of causing him injury. Charlie silently investigates the former officer's claims to help restore Rex to the force. Jesse's firearms skills get him an invitation to join SWAT.
A reality game creator is murdered by a venomous Black Mamba snake. Charlie and Rex search for the killer while Sarah overcomes her fear of snakes and eventually captures the snake. Jesse secretly sets up Donovan on a dating app.
Charlie and Rex respond to a women's prison break allowing a convicted murderer and an incarcerated ex-cop escape. During the investigation Sarah discovers systemic abuse in the prison infirmary.
A student is found murdered by Donovan's daughter Camilla at a college rave. Charlie, Sarah and Jesse work to find the killer while stumbling on Camilla's meddling to get the story for her journalism internship.
Sarah's arson court testimony undermined by colleague. The team has 48 hours to discover the truth before suspect released. Sarah and Rex re-examine evidence, uncovering manipulation that solves arson and murder.