The episode begins with the flight attendants find the dead body of a woman in the restroom of an LA flight. Her eyes and nose are bleeding. The flight is about to land. The suspect’s name is Dr. Jarrod Prodman and he is traveling in flight no. 792; but he is traveling under the name of Benjamin Gallagher to remain unidentified. He has a female companion and is carrying a biochemical weapon; a deadly small pox virus. Eric and Nell are trying to reach Callen and Hana; but the equipment is acting up. But Eric manages to set it straight. This time the Five O team is flying with the NCIS LA team. They are working on this case together. Kensi and Deeks are at the airport and ask them not to let the passengers de-plane; but they already have.
They had to let the passengers go as they had to remove the dead body. This is news to Kensi and Deeks. They see the body and inform the others. The woman’s name is Sharon Walker. The only thing that links the doctor and the victim together is that they stayed in the same hotel in Hawaii. At the airport, Kensi and Deeks are looking for Jarrod, but Eric tells them that he left. He did not go to the baggage claim and left six minutes ago. Eric educates Kensi and Deeks about Prodman. He is a renowned epidemiologist, but was disgraced in 2007 for cooking up data to pump his research. But there has to be someone paying for all this. Prodman is broke and has no source of income. The NCIs team introduces Danny and Ho to the rest of the team. Danny’s sarcasm isn’t appreciated much. Hetty has a word with Callen and Hana in private. She tells them that if this leaks out, there would be chaos. Hetty announces that Deeks and Kensi need to get inoculated; but Deeks isn’t a huge fan of needles. And Hetty manages to make Deeks cry out loud. He passes out.
Kensi and Deeks arrive at Sharon’s house. Sharon’s twin sister opened the door. They look exactly the same; so much that even Kensi was confused for a moment. They break the news to her. Meanwhile, Hana, Ho, Danny and Callen check Prodman’s hotel room, but they don’t find any leads, as the room was rented out for just a day. They figure out that Sharon’s death wasn’t a planned one. Just then they spot Prodman and Ho and Hana chase him and pin him down. Next, Hana and Callen are interrogating Prodman. He wants a lawyer. Prodman tells them that he didn’t know it was small pox; he thought that it was some sort of a research. He adds that Sharon had cancer and thinks that she could have been relapsing. He stole her personal belongings because he panicked. But obviously the detectives don’t buy his story. They show him a video shot at the quarantine centre, where Prodman was documenting the progress of the disease.
Prodman has nothing to say. Callen finds lots of money in Prodman’s bag. They want to know who is paying him off. He tells them that her name is Dr. Rachel Holden. Eric and Nell find out more about Holden. Meanwhile, Prodman tells the duo that Holden met him at the hotel, gave him the money and that was the end of it for him. He doesn’t know who is she doing it for or who the buyer is. They get an address for doctor Holden. Kensi and Deeks go to the hospital to find out more about Holden. The hospital wants to discuss the entire thing with their legal counsel before they talk to the cops. So Deeks decides that they should play doctor and nurse- Deeks dresses up as a male nurse and so obviously, Kensi is the doctor. Deeks manages to sneak into Holden’s room and finds a message written on the white board. He is stupefied. At the office, Nell tells Eric that Holden hasn’t used hr credit card for several months, but the last two purchases were plane tickets; one for Prodman and the other one for her, that will leave from LA the next day.
She is going to Costa Rica. So whatever she is doing with the virus is going down today. But they don’t know when and where. Just then Eric tells Nell that if the person who is handling this virus knows about its deadly effects; they also might have access to the vaccination; which means, the person would have to steal it from military or State Health department facility. They find out that two weeks ago there was a break-in at the State health facility center. Nell finds out the man who is responsible for the break-in at the health center; his name is Gabriel Marchal. He is linked to several unsavory groups; the ELE. Both the teams are keeping an eye on the suspected area. They locate Gabriel. But they have to clear the area without causing chaos. They are successful in doing so. They search the van they were expecting to find the virus; but its not there. They arrest Gabriel.
But he denies exchanging anything with the doctor. Nell tells Callen that Holden had wired a large amount of money into one of her accounts six weeks ago. Eric tells Hana that he did not find anything in Holden’s computer hard drive. But there were few of her articles related to work. But it is the nature of those articles that is a little disturbing. In one of her latest articles, she says that a pandemic is the best way to control population. She thinks that by eliminating small pox from the planet; we have eliminated nature’s life balancing systems. She thinks she is doing God’s work. According to Holden, the best way to save the planet is to naturally thin out the human herd. Nell has an important finding. Holden had bought some supplies, which Nell thought is for business. But then she bought around 300 t-shirts for school children.
So, she would distribute the infected t-shirt in a school, the students would take the infected t-shirt back home and infect their families as well. Kenzi remembers seeing a group of students at the airport. They find out about an international gathering and they decide to shut it down. But its too late; the convention started an hour ago. They go to the convention center. They find out that there are free t-shirts being distributed. They locate Holden and announce themselves. But she runs. She tries to escape in her car, but the teams manage to get hold of her. They also find the vials. They arrest Holden. She tells them that the earth is dying and its we who are the disease. She was just trying to help.
At the office, Nell tells the group that the Health Department and the CDC are vaccinating all the people who might have come in contact with those bags and t-shirts. Hetty thanks the Five O team on behalf of NCIS. Danny and Ho leave to catch their flight. Both the teams managed to save the earth. The episode ends.