An undercover agent's death leads to the unit's investigation into drug overdoses involving a porn website that specializes in girls who just turned 18. Meanwhile, Rusty finds out that his biological mom is pregnant.

The Feds and Major Crimes search for a possible terrorist when they discover that an ISIS-styled beheading of an American military veteran is filmed in Los Angeles. Meanwhile, Sharon has an idea to help Buzz with a bad evidence video.

Det. Julio Sanchez's application to become a foster parent is jeopardized by his reactions to a particularly gruesome murder after the Major Crimes Division finds a chopped up body burned to bits in the barbecue pit of an L.A. Park.

While investigating a murder that has personal implications for Sanchez, the squad uncovers a much larger criminal operation. Meanwhile, Buzz comes face to face with someone that may have been present at his father's murder.

The Major Crimes unit continues to investigate the conspiracy behind Dwight Darnell's murders and his links to the Zyklon-Brotherhood. Sharon Raydor, disturbed by her own reactions to the case, seeks penance in the Ritual of Confession.

When Captain Sharon Raydor and the Major Crimes Division investigate the murder of a young woman found in the L.A. River, their case is impeded by a secretive P.I. working for a tech industry millionaire and by Deputy Chief Winnie Davis.

When Major Crimes discovers a young one-man-geek-squad in the middle of his Atwater living room with his throat cut, suspicions swirl around his roommate and some unwitting customers, all of whom he was blackmailing.

A murder case goes sideways at trial when defense attorney Linda Rothman is able to destroy Det. Amy Sykes's credibility on the stand. Helping Rothman as a defense investigator is Amy's old nemesis, Mark Hickman.

Sharon's son, Ricky, comes home for a surprise visit while Major Crimes investigates what looks like the "follow home" murder of a retired LAPD fraud detective, who may have been murdered for an arrest she made decades ago.

A murder investigation turns explosive while Captain Raydor duels with Chief Davis for control of her case as she and her squad try to determine if they are dealing with a terrorist. Meanwhile, Rusty gets some alarming news from Gus.

After discovering the identity of the bomber her division has been searching for, Sharon Raydor and the Major Crimes squad struggle to determine his next target as Major Crimes heads for an explosive season finale.