Season 4 - Episode Guide

With Gibbs retired and boat-building in Mexico, the NCIS team must learn to work without him when Ziva is wanted by the FBI after she witnesses a political assassination.

Gibbs is temporarily reinstated at NCIS when his friend's life is threatened by an escaped convict.

The NCIS team is called to investigate a bloody, abandoned car registered to a missing Navy lieutenant.

Gibbs and the team investigate when the body of a Petty Officer is found in a car shot at close range.

The NCIS team is called to investigate when a real estate agent finds the body of a missing Lance Corporal is found in a vacant house.

Gibbs and the NCIS team investigate when a Marine is attacked in his home and his daughter is apparently kidnapped on Halloween night.

Gibbs and the team investigate a suspected terrorist attack at a military country club that kills a Marine Colonel.

When suspicious activity surrounds the death of a decorated Marine veteran, the NCIS team works to clear his name.

Forgoing NCIS procedure, McGee risks his career when he takes matters into his own hands after his sister appears at his door bloodied and confused.

The NCIS team is called in when the burnt and mummified body of a wanted man is found in a furnace on a Marine base.

The NCIS team investigates the death of a Navy Lieutenant who was working on a high level project for the Department of Defense.

The NCIS team investigates when a high-level Marine intelligence officer is found murdered in a small town motel room.

The NCIS team must track down a wanted terrorist who has obtained a missing, highly toxic chemical weapon.

Ducky comes out of the autopsy room and goes undercover to stop the illegal sale of the Navy's top secret weapons system.

The NCIS team investigates when the body of a young sailor is found in an abandoned building in a seedy part of town.

The NCIS team suspects foul play when a Navy Lieutenant is the victim of radiation poisoning.

Gibbs and the team look for a potential serial killer when an explosion at a military cemetery mausoleum reveals a cache of dismembered human remains.

With the young Marine on life support, the NCIS team tracks his movements in the days before he was left for dead and discovers a secret trip to Baghdad via a private cargo plane and a link to Gibbs' past.

The NCIS team discovers a tip about terrorist activity was a trap that resulted in the death of two agents. Blaming herself, Agent Cassidy works with the NCIS team to track down the people responsible.

McGee is horrified when a Petty Officer on whom he based the character for his latest book is murdered. With little to go on, the team pushes McGee to figure out who could have accessed his secret manuscript.

Director Shepard takes a huge risk and agrees to meet an informant alone, but the meeting goes bad and her contact is killed. Gibbs and the NCIS team attempt to gather the information the man was going to supply or risk losing their nemesis once again.

With little evidence, the team turns to Scott to re-create the scene of the crime using his heightened senses of hearing and scent to track down the Petty Officer's killer. Meanwhile, Tony and Gibbs struggle with personal relationships.

Gibbs ignores the bureaucratic paperwork associated with his "acting" director duties and leads an investigation for a murder victim found in a taxi headed to NCIS headquarters. Meanwhile, Jenny discovers a secret about her past.

As the NCIS Director returns from a controversial European junket, and Gibbs and his agents reluctantly prepare for hastily announced Homeland Security polygraph tests, tightly woven secrets among the team unravel, revealing the biggest surprise in this Season of Secrets. In addition, an unarmed Dinozzo and his girlfriend are held captive by a merciless drug-dealer.