Trama

At the high school at Quantico, students and teachers fall asleep while in class; Gibbs and company investigate; one girl disappears. A grandfather both helps and interferes. Temp interns join. The gang solve the case and find the girl.

At the DoD high school aboard the Marine Corps Base, Quantico, Virginia, students and teachers fall asleep while in class; Gibbs and company, augmented with three short-term interns from a nearby university, investigate; Tony and McGee find a cylinder of gas connected to the ventilation system. After the evacuation of the building, one student, Rebecca, is absent; the team start looking for her, and they call the FBI. Gibbs meets with Mason, Rebecca's paternal grandfather, who starts acting on his own, and who presents a curious background; Mason slips away, but the gang later find him; then Mason tells Gibbs about his true history. Abby and her intern produce. Attention turns to the teacher, who turns out to be something else. Gibbs, Tony, McGee, and Ziva meet with Mason and the teacher, and the gang find Rebecca.—DocRushing

A teacher (Sam Anderson) leads an inattentive class on "Paradise Lost." He rouses one sleeping student with an air horn, but soon they're all putting their heads down on their desks and he's stumbling and gasping for air, too.

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McGee leads Waverly University students on a tour of the office. Tony thinks interns are a bad idea, because it feeds McGee's need for groupies. They're staying for the whole week. Gibbs hands out assignments. The case of the week is a gas leak at Quantico.

Duckie's intern Sarah insisted on tagging along, even though there's no body. He's irritated, then she begins a story with "this reminds me of a time..." and they're instant pals.

McGee shows his, Conrad, to the source of the problem, a gas tank hooked up to the ventilation system. Conrad is already ready to bail. He's a finance major and this was the only class that fulfilled his public affairs requirement.

Ziva talks to the teacher, who instantly recognizes her student head count is one off.

She's Rebecca Mason, 13, who lives in base housing with her parents, who are both deployed. She stays with her grandfather, who's on his way in.

Gibbs talks to Nicolas Mason (William Devane), who says Rebecca's mother just came into some money. He's pessimistic about NCIS finding his granddaughter. Gibbs leaves when Mason answers the phone, saying it's Rebecca's dad.

In the lab, Abby briefs her intern on the rules of the lab, which allow her to keep an eye on him at all times. She tries to get him to put on bells.

She tells Gibbs there were no fingerprints on the gas cylinder, but there was a boot print. She's never heard of the compound in the cylinder, which means they're looking for a chemist.

McGee makes his intern do grunt work. Tony tells Gibbs he'll "keep trying" to contact the girl's parents. Gibbs realizes her grandfather lied to him. Ziva tries to call Gramps, but doesn't even get the FBI who should be at his house.

McGee finds a Skype record of the call he took in front of Gibbs. They listen to it. It's a scrambled ransom call asking for $500,000 in cash and telling him to come alone.

The team arrives there 10 minutes after the drop.

Gibbs and McGee check out the alley and find a body -- but it's not Mason.

At the office, they find the dead guy is Eddie Lang. Forensics confirm he was the kidnapper.

McGee looks into Mason's background and finds it's all fake -- but he's not in any of their retired spy databases.

Mason calls MTAC.

McGee says Mason is using fancy routing equipment to hide his call. Mason says it was self-defense. He warns Gibbs the kidnappers can't be trusted. He turns down Gibbs' requests to come in.

"You have to work within the law, I am a bit more flexible," he says.

Palmer reports to the morgue and finds Duckie harmonizing a Scottish song on with Sarah. Palmer's put out he missed out on a crime scene.

Duckie reports to Gibbs that the victim's neck was broken and he sports injuries that are from self-defense moves.

Tony wonders aloud why Gibbs is suddenly willing to have interns around. McGee found a DVD in the kidnapper's car. It shows a crying Rebecca in a bedroom and the day's newspaper, proof of life. Seconds later, a virus tears through McGee's system. It sends the NCIS phone number over the internet and the phone quickly rings.

Gibbs tells the kidnappers a family member intercepted their first call. They raise the price to $1 million and give them 24 hours. McGee finds someone else was trying to trace the call. They assume it's Mason.

They head to the address and find another kidnapper dead, tied to a chair, bloody, with pliers nearby. "This was not self-defense," Ziva says.

Palmer tries to make himself useful, reporting that Mason's prints were all over the trailer. Tony goes into MTAC with Gibbs to talk to Rebecca's parents.

Gibbs says they'll go along with the ransom, but they only have half that. Rebecca's dad asks what his dad has done. He doesn't know his background either. There's a lockbox in the floor of Mason's bedroom.

Gibbs goes into the evidence locker and takes out a box of cash. Conrad sees him while he's sweeping nearby. He points out Gibbs could get in a lot of trouble and asks why he's doing it. Gibbs says it's his job.

Conrad asks why Gibbs is allowing interns, asking what's changed. "I dunno, maybe me," Gibbs says.

McGee goes through Mason's box, which has super secret stuff in it like satellite access codes and old presidential itineraries. Palmer tries to insinuate himself in the investigation and gets slapped back.

Abby intern comes up with news. He's wearing his bells.

In the lab, Gibbs smells hamburgers. Abby has found a new patent for scented billboards, the compound for which is similar to the gas used. The chemist works at Greystone chemicals.

Outside the Greystone building, they see Mason inside. They go in and there's already a body on the floor. He fights off McGee and Ziva but quits when Gibbs tells him to. He tells Gibbs the victims aren't kidnappers. "They're part of my team, and whoever did kill them is playing us all."

Conrad and McGee watch Mason through the two-way glass as he inspects the interrogation room for a way out. Gibbs asks Mason who he is and Mason says Gibbs isn't authorized.

He thinks about it then says he and his team were part of an off-the-books experiment, doing the things that needed to be done. There were eight, then three when the project was canceled two decades ago. They were ordered to never make contact again, but he went to them when Rebecca was kidnapped.

He knew the Greystone gas from past operations. The guy in the trailer was his comm. specialist. He brought him the cell phone for him to trace it. He figures his team was the target and this brought them together.

Watching, Conrad worries that Rebecca might really be dead.

Tony tells Gibbs they have a request to drop all the charges. Gibbs agrees. Abby found a small tear in Mason's engine block, which was rigged to blow. They found prints on it.

They belong to Walter Carmichael, the substitute teacher from the opening and a member of Mason's team. Mason thought he was killed in Sri Lanka in '87.

McGee already checked out Carmichael's place. They wonder about motives.

Duckie goes over Carmichael's faked past as a missionary. He thinks Carmichael felt guilty. They found self-torture devices at his house. Duckie thinks his final act was the murder of his team mates.

Carmichael calls. He doesn't care about ransom anymore, he just wants Mason. Gibbs says they'll give him what he wants.

The team takes a handcuffed Mason to a public square, where Ziva takes a sniper perch. Carmichael blends as a homeless man, then confronts Mason. He says if they don't let Mason go, they'll never see Rebecca.

Mason undoes his cuffs and steals a gun, he aims it Carmichael, demanding to know where Rebecca is. Ziva shoots Mason.

When Carmichael sees him down he tells them Rebecca is in the trunk. Gibbs yells at Ziva, asking why she took the shot.

Carmichael says Rebecca was never in danger because collateral damages were one of their sins. They get Rebecca out of the car and Mason pops up. Ziva's bullets were blanks, Mason was rigged with corn syrup.

Back at the office, Rebecca is reunited with her parents and previously uninterested intern Conrad suddenly understands the appeal of being an NCIS agent. McGee hands him an official internship application.