Trama

Within 30 miles of Washington, DC, eight kids in Navy and Marine Corps families have suddenly become badly ill, requiring treatment in ERs and ICUs; Gibbs and company investigate; Carol, of the Naval Medical-research Center, joins the effort; immediately the number of sick kids grows to 14, then 19, 23, 28, and 34, and none of them responds to treatment. Duckie announces the first fatality, who was a veteran of Vietnam, then he describes the cause of death and the treatability in the kids. Abby says that she has misidentified the particular nature of the illness, so she, Jimmy, and Carol keep working, and they eventually nail it. Abby gives Jimmy a lecture about kindness, optimism, and parenthood. Then the gang identify an international traveler who in many places has recently encountered many kids and the fatality. Meanwhile Vance has three tense chats with his estranged father-in-law and then a nicer one.—DocRushing

A Marine comes home for the holidays to see his wife and two kids. He goes to check on his young daughter Emma, who came home early from school with a fever. When he touches her, she's burning up. Her parents try to rouse her, but can't.

At NCIS, Tony is looking forward to spending his Christmas in Jamaica. Ellie is going home to Oklahoma where her husband and brothers will argue about football.

Abby presents them with her lab-baked holiday cookies. McGee gets off the phone and reports about Kevin and Audrey Daly and their daughter, Emma. She's in the ICU. Ellie recognizes the symptoms as McGee describes them, the same thing happened to her Marine friend's son, who's now on a respirator.

Gibbs comes in and reports there are eight sick kids total. Abby's oldest friend Carol, who works at the Naval Medical Research Center, is with him.

Abby worries it's bioterror. Carol and Abby will coordinate with the CDC while NCIS works the case.

At home, Vance checks on his own kids before he takes them to school. Outside, Vance isn't happy when he sees an older black man named Lamar Addison on his lawn. Lamar assures him he's not looking for trouble, as he extends a hand, but Vance is angry and suggests he return to New York. He tells his kids the man is nobody.

At the hospital, the total of sick kids has reached 14 and none of them is responding to treatment. Tony calls and says there are five more cases at Washington General in the last hour.

At NCIS, Duckie is impressed by Palmer's epidemiology knowledge from classes he took after Tony got sick. He suggests Palmer help Abby and Carol pour through the data.

In Vance's office, he tells Gibbs about Lamar Alexander: he's Jackie's father. He owns a chain of car dealerships in New York and walked out on Jackie and Michael when they were kids.

Palmer's wife Breena stops by the lab to tell him the agency may have found them a birth mother to meet with. He's excited, but that's interrupted by Carol isolating the pathogen through a microscope. It doesn't look like anything they've ever seen.

Back upstairs, the number of sick kids keeps rising. Gibbs calls everyone to the big screen for an update, but Ellie stays put to follow a lead -- not knowing they always meet around the screen in the second act.

Ellie gets a name from a government watch list: Max Comey, a scientist fired for stealing mold samples. He lives on the same street as a school four of the kids attend. He also got in a fight with a Marine recruiter last week after he was rejected.

Tony, Gibbs, and Ellie go to Max's apartment, but it's completely empty. Gibbs finds a biohazard bag in the trash. Duckie calls to report the illness caused a death of an elderly person. The victim is Lloyd Grunfeld, a Vietnam Vet who managed an on-base dry cleaner.

There are now 28 sick children.

Max's coworkers say he was egotistical and thought highly of himself.

Down in the morgue, Duckie tells Gibbs that Lloyd died of aggressive pneumonia. Palmer starts to worry about having kids at all, given the fear over things going wrong. Abby and Carol work to ID the strain.

Vance has Lamar brought into his office after his nanny called to say Lamar was at his house. Lamar wants to get to know his grandchildren, but Vance tells him Jackie always told them their grandfather was dead and he doesn't intend to say otherwise. Lamar offers to pay for the kids' college if he can meet them but Vance bristles at the idea he's trying to buy them. He throws Lamar out.

Down in the lab, Abby and Carol have ID'd the strain as strep pneumonia and the hospitals are going to start administering the right drugs.

Back upstairs, they're reviewing video of the kids to see where they might have picked up the germs.

McGee gets word that Max Comey has been located. Gibbs wants Ellie to approach him since he fancies himself a ladies man. She flirts him up at the Christmas tree lot where he's working. She says she temped with him and flatters him. "They'll know they've made a mistake soon enough, I'll show them," Max says.

The team comes out and searches Max's van. They find a biohazard cooler in it.

Back in interrogation, Max says the lab was throwing away the mold spores. Max says he kept them to do his own experiments. Max says he was planning to make his girlfriend Bernadette sick so he could cure her to make her appreciate him.

Later, Duckie thinks Max is completely delusional and Bernadette probably isn't even his girlfriend. Abby comes down with bad news, that the illness is not what they thought and the kids aren't responding to treatment.

Gibbs calls Vance at home to update him. Vance's doorbell rings, it's Lamar. He has one thing to get off his chest. Vance hears him out. Lamar says he left Jackie's mom Millie because he felt too young to handle the responsibility. He later had his own family and raised three wonderful kids. Then he got a letter from Jackie last Christmas.

Lamar says he's just worried about the kids' safety. Vance points out the card Lamar got is an unsigned Christmas card, and even their mailman got a more personal note. "You've got regrets, that's on you, but it's not up to me and my kids to make them go away," Vance says.

In the lab, they're now confronted with lesions the kids are developing. Palmer insists on staying for the all-nighter, even with the meeting with the birth mother tomorrow.

At the hospital, McGee gets word the number is up to 34 sick kids from eight different hospitals, from Portsmouth to Baltimore. They can't find any crossover.

Gibbs notices the candy stripers, dressed as elves heading home. He gets an idea.

Back at NCIS, the team has spent all night cross-checking volunteers at base holiday markets. All of the kids attended one.

Vance drops in on the lab. The lesions are now turning purple, which prompts Palmer to say he's never having kids. Abby gives him a lecture on how good things like optimism, compassion, and faith are supposed to be infectious at the holidays. Vance takes note when she lists forgiveness.

Gibbs conferences in to ask if the disease could be African. They've narrowed patient zero down to the Marine who played Santa at all the holiday parties -- who also took his suit in to be dry cleaned. He just returned from Congo. With Africa as a parameter, the lab geeks identify it as meningococcal A, which is treatable, and begin alerting the hospitals.

At the hospital, the Dalys watch as Emma wakes up. Jimmy and Breena meet with the birth mother.

Vance introduces his kids to Lamar, their grandfather.

Ellie shares her mom's coffee cake with Gibbs before he leaves for the airport, saying it always makes her happy and everyone deserves to be happy at Christmas.