In the aftermath of Kate's death, the team confront their emotions over the tragedy while Gibbs is determined to hunt down Ari.
Ari uses the team as pawns in order to continue his game with Gibbs.
Gibbs matches wits with a serial killer he put away 10 years before when the man, who is scheduled for execution, doesn't reveal some crucial information he had promised to deliver.
Gibbs and his team investigate a recently dead corpse found encased in a Civil War-era iron tomb.
When a Naval Petty Officer is brutally gunned down on the freeway, the team discovers that he had been leading a double life.
The NCIS team investigate the possible murder of a bored housewife who had been running an Internet sex site from her bedroom.
The NCIS team work to find a Navy officer who went missing while working as a liason to a defense contractor after his young son is left behind.
Tony and Ziva assume the identities of two assassins whose bodies were delivered to NCIS in an effort to find out who the killers were targeting.
The NCIS team rallies to clear Tony's name after part of a female body is found at Quantico and the evidence points to Tony as the main suspect in the woman's murder.
McGee finds himself under investigation when he shoots an undercover officer while on assignment.
The team investigate the murder of a super-model who was murdered while filming a reality show on a Marine base.
Tony and Ziva are trapped in a container at a shipyard after they are ambushed while conducting an investigation concerning weapons smuggling.
The team must locate a Commander in charge of nuclear weapons who has been abducted.
Gibbs and the team suspect that the murders of two Marines' wives were racially motivated and that the killer may strike again.
The team discovers the severed head of a Marine when they bust an illegal automotive chop shop.
The NCIS investigates the mysterious explosion of an ambulance that was transporting the remains of a Marine.
The NCIS team searches for a missing Marine when some dog tags are discovered in a national forest area.
The NCIS team is called in to deal with a teenager who has strapped a bomb to his body and is holding fellow students at a high school on Quantico Marine Corps Base hostage.
When group of kids come across a body frozen in a lake, it's discovered to be a missing Marine and the NCIS team is called in to investigate. They then find three more bodies riddled with bullets.
A Pentagon cryptographer who was suspected of being a spy is found dead, an apparent suicide. Gibbs and the team are called in to investigate and discover she was not alone at the time of her death, that she may have been murdered.
The NCIS team discovers a grisly murder scene and when some contaminated evidence almost kills Abby in her lab, they realize that the scene was staged, that Abby was the intended target. Later the team reveals some seedy characters in Abby's past and must work swiftly to determine exactly who's trying to harm her.
Ziva uses a routine subdue tactic to restrain a suspect but later, when the suspect dies, Ziva becomes focus of the investigation behind his death. The victim’s brother kidnaps Director Sheppard demanding the release of his brother, not knowing he's dead. Abby and Ducky work to try clear Ziva's name.
Gibbs is injured in a terrorist attack leaving the NCIS team distraught. The team must suppress their feelings about Gibb's injuries and continue to work the case. Feelings of resentment emerge among the team toward Tony as he steps into the role of senior officer. While Gibbs is recovering, he's overwhelmed with memories of his past that he had long struggled to repress.
As the team tries to track down the terrorists behind the bombing that injured Gibbs, they learn that the terrorist group is planning another bombing of 9-11 magnitude -- and that Gibbs has information about their plan. Meanwhile, Gibbs receives a visit from his former boss and mentor that conjures up suppressed memories. As Gibbs regains his memory, he finds himself on a race against the clock to fill in the gaps and stop the terrorists.