e svém bytě je nalezena zastřelená kryptoložka. Protože armádní velení má informace, že právě z tohoto oddělení unikají informace, má vedení NCIS za to, že žena byla špionem. Jenže pitva odhalí, že žena byla zastřelena ve chvíli, kdy byla v bezvědomí. Stopy vedou k zaměstnanci venezuelské ambasády a NCIS ho dlouho považuje za vraha. Problém je jak ho zadržet. Gibbs však na poslední chvíli přijde na to, že skutečným vrahem a zároveò skrytým špionem je někdo úplně jiný.

Tony and Ziva arrive at Lieutenant Hill's home. She is a cryptographer with the Pentagon that missed an interview with them earlier that morning and didn't show up for work. They need to interview her regarding espionage. When they go to the door, there is no answer so Ziva and Tony head around back. Ziva peers in the windows as Tony teases her about it. When they get to the back door, Tony jokes about shoving Ziva through the pet door then freaks out and whips out his gun when a cat comes out the pet door. Ziva teases him back and asks him if he's afraid of a little ***** cat. Tony nods his head down for Ziva to look down. She sees bloody paw prints left by the cat.

The team arrives to process the crime scene. They discover Lt. Hill lying on her couch with a gunshot wound to the head. The initial assessment is Hill committed suicide. Gibbs finds the bullet went through Hill's head and lodged into a book in one of the bookcases in her living room. Gibbs tells Tony to catch the cat as it's evidence and hands him the cage then leaves the room when Ziva calls him. Tony hands the cat carrier to McGee and tells him to catch the cat. McGee explains he's allergic to cats but Tony tells him to do it anyway.

Gibbs joins Ziva in the bedroom and she shows him roughly $60,000 in cash taped underneath her desk. Tony comes in and jokes about the "nerd" having stuffed animals in her bedroom. Ziva says there is nothing wrong with it as she had stuffed animals too, when she was 12. Gibbs remarks that for a woman about to commit suicide, Hill certainly took the time to make her bed. Back in the living room, the cat runs by Gibbs and hides near the bookcase. McGee comes in with his nose all red from allergies and Tony smirks. He and McGee agree to corner the cat but Gibbs grabs the cat carrier, puts it on the floor with the door open and yells "Hey!" The cat looks, Gibbs points to the carrier, the cat runs into it and Gibbs locks the door.

Gibbs and McGee head to Hill's office at the Pentagon (Gibbs brought McGee for the "geek speak") while Tony and Ziva remain behind. Tony is playing with the cat in the carrier when it hisses and nearly bites him. The NCIS team removing the furniture for evidence start laughing and Tony gives them this huge speech about how the cat is the one who killed Hill by feasting on her face. Ziva tells him to get back to work then notices the cat is gone again. Gibbs and McGee arrive to inform Hill's supervisor, Captain Kevin Dorn, of Hill's demise. The Captain immediately puts his office on lock down and has them all save what they are doing and confines them to quarters until they are interrogated.

Back at the lab, Abby reenacts the crime scene for Gibbs using McGee to play Hill's role. She explains how the blood should have splattered but they do not see it until Abby turns on her fluorescent light and they see the left side blood splatter with two partial footprints in it. They realize that someone else was there and it was murder, not suicide. Ziva and Tony review the evidence and possible scenario. McGee returns with the world’s greatest barbecue, which Tony does not get to eat because McGee discovers a fingerprint match on the gun. Tony and Ziva are sent to pick up fellow cryptologist Keira Napleton. Gibbs eats Tony’s dinner for him.

In interview Napleton explains that she was the victim's temporary roommate and expresses surprise that Hill shot herself with the gun she owned. Napleton was at her boyfriend's the night before the shooting and went straight to work.

Captain Dorn comes to the bullpen to report that a “memory doodah” is missing its memory card. Only two other people had access to them, Hill and Napleton. The team returns to Hill’s in search of the missing card. Its late at night and eventually only Gibbs is left awake and searching, and he finds it in a box of cereal.

When Ziva and Tony arrive at Abby’s lab McGee is asleep at the table, Tony of course wants to superglue him to it. Gibbs arrives just in time to headslap him and get the fingerprint results from the card. It’s a Venezuelan official, Simon Roca, with diplomatic immunity. Gibbs contacts the State Department to try to get access to him, but he is untouchable. They are not allowed to question Roca, but Gibbs sends Ziva and Tony to keep tabs on him, when McGee finds out he scheduled to fly home.

While watching for Roca, Ziva offers to give Tony piano lessons, but Tony is stuck on the idea of Ziva being a “screamer.” When Roca’s car leaves the embassy they follow it, with instructions to delay him. Ziva’s plan is to hit him. But the car was a decoy, Roca got to the plane another way. McGee tries to stall takeoff, but they don’t have enough time.

Ducky arrives late, with his mother in tow, as Abby and Palmer are about to start the autopsy without him. Mrs. Mallard confuses the dead body with their former housekeeper and instructs Palmer to get her a drink. Ducky hands mother Mallard off to Abby so he can get to work. Mrs. Mallard is quite taken with Abby despite the fact she reminds her of a sister she hates. She later attacks MTAC with her cane and makes a pass at Gibbs.

Ducky has discovered that Hill was unconscious before she was shot. McGee is working on decoding the flash card but needs help from someone within the crypto unit. The Captain suggests Napleton, but Gibbs tells him she is still a suspect. The Captain wonders why, saying that Hill must be the mole why else would she shoot herself. Gibbs immediately heads to Abby. He wants her to check the cereal box for GSR, he doesn’t think Hill put the card there.

Back in the bullpen Ziva is attempting to persuade Tony to take responsibility for the car accident. She already has 3 on her record. She gets very close and promises anything. Tony gives her up to Gibbs though, and gets a headslap. The Captain and the team head up to MTAC. On the way Abby whispers to Gibbs that he was right. Gibbs confronts Captain Dorn about knowing that Hill was shot. Outside of the team only Napleton knew. McGee notes Dorn was the one who let them know about the missing card, the only evidence that tied Roca to the murder. Dorn killed and framed Hill, with the diplomat to take the blame, perfect until he slipped up in front of Gibbs.