Gibbs and Franks investigate the disappearance of a young Marine connected to a mysterious compound with a charismatic leader, and Lala's fate is revealed.

When the body of a college swimmer washes up on the beach, the team must determine if it was an accident or murder. Meanwhile, Gibbs prepares for his first interrogation.

When Dr. Donald 'Ducky' Mallard, a liaison from D.C. headquarters and an old acquaintance of Gibbs, arrives to evaluate whether Pendleton needs an in-house medical examiner, not everyone trusts that's the real reason behind his visit.

The team investigates the robbery of a Navy bank while Franks' brother blows into town desperate for help after hitting rock bottom and Lala, still struggling after her accident, makes a decision about her future.

When a naval officer mysteriously dies, the team travel to the small dust-blown town of Serenity, where they encounter secret-harboring residents, an uncooperative sheriff and an investigation that will reverberate for decades.

When an anonymous tip leads to the body of a young Marine at a horrendous crime scene, Randy believes there may be a connection to a previous case where a coin was left in the victim's throat.

The team investigates the murder of a Marine who had recently been handpicked for a classified mission as Wheeler's personal life is upended, Lala is thrown by unexpected news from Vera, and Gibbs and Diane double-date with Randy and Junie

After CI shooting, team works with Oceanside PD to find culprit. Frank visits brother Mason at compound while Gibbs faces challenges with Diane's LA job.

As the team discovers Gibbs' drunken Vegas elopement with Diane, the newlyweds contemplate their future; the team investigates a fatal movie theatre bombing with a connection to the Pruitt compound where Franks' brother Mason is staying...

When a marine captain shows up at Camp Pendleton exhibiting symptoms of a fatal virus, NIS goes on lockdown and Gibbs is forced to take charge. Team races to determine whether it really is a deadly outbreak or something else entirely.

Mary Jo reconnects with an old friend from Atlantic City to investigate two Marines' roadside deaths when the NIS Regional Director attempts to transfer her.