The episode begins with a man frantically banging at the door of a house. The mother and the children are scared. The mother calls 911 and tells them that her ex husband is trying to break into the house. The cops arrive and announce themselves; the man comes out and the cops are horrified when they see his face-his face is covered with large boils filled with puss. He asks for help. Next, we see that Danny is at Steve’s residence; going through his things. He finds a map with a location marked on it. Just then Ho arrives. Danny shows him the map and tells him that Steve has gone to Japan. Ho tells him that Shel Burne could be the answer to a lot Steve’s questions; including about his father’s death.
Just then Danny receives a call from the Governor and the two leave. They arrive at the scene and Kono too joins them. Ho tells Kono that a strange husband bangs at the door of his house and then drops dead when the HPD arrives. He had hemorrhaging small pox; a rare disease. But that’s eradicated. Danny tells her that the Governor wants them to investigate the case discreetly, while the CDC determines as to how the guy got the disease. The CDC has incinerated the body and Kono wonders how to begin with the investigation. Max tells them that he has the blood and tissue samples; and also the guy’s pictures. The victim’s name is Bryan Palmer and he was honorably discharged from the army ten months ago. Ho wonders that if the guy is from the army then he should have been vaccinated; but Max tells him that the vaccination could have worn off, as it is effective for 3-5 years.
Danny wonders as to how Bryan got infected with an extinct disease. Max tells him that the only two places where the small pox virus is stored is CDC and a place called Vector in Russia. They suspect it to be a terrorist activity. Max also adds that Bryan must have been exposed to the virus in the past two weeks. He thinks that Bryan wasn’t infected the traditional way but was injected with the virus. He says that if Bryan had been walking around with it for too long, then within a few weeks the entire island could be infected. Danny and Ho meet Bryan’s wife, who is kept in an isolation ward. She tells him that Bryan moved out a couple of months ago. But they were trying to work things out; but then he stopped coming for family counseling and would not return phone calls.
She tells them that Bryan would have occasional bouts of drinking, where he would shut himself up and not talk to anyone. Ho decides to check Bryan’s room at the Breakers Hotel. Danny finds some syringes and some sort of a liquid with it. But Kono educates them that the drug they found in Bryan’s room is an antidepressant and the injection mark is due to the same. But his autopsy doesn’t show any trace of the antidepressant. Kono finds out the name of the pharmaceutical company who are conducting the trials, Biostratum; but they don’t know who the participants are. But the local project manager, Ken Tanner, could tell them who the participants are. But Tanner hasn’t shown up at work today.
Meanwhile, the HPD calls and tells them that they have found the co-ordinates of Bryan’s cell phone location; its active. Kono tracks it down while Danny and Ho go to Tanner’s residence. But they find him dead in his car in the garage. They figure out that Tanner was murdered. Kono goes to the location, and finds Bryan’s cell phone and clothes wrapped in a plastic bag; it has a biohazard label on it. Danny informs Ho and Kono that Tanner was killed by a man named Dracul Comescu; his prints were found on Tanner’s car and keys. He is a Romanian national and is on the NCIS watch list for some special projects in LA. Danny calls Hana from the NCIS team and asks him about Dracul. Callen is surprised that Dracul is in Hawaii and tells Danny he also has some personal issues with him. Danny informs them that Dracul has gotten hold of the small pox virus.
Meanwhile, Charlie tells Kono that he has found clothes of different sizes in the plastic bag. It means that there are other victims too. Callen and Hana arrive in Hawaii and they meet the team. Kono tells them that they have found three other sets of DNA from that plastic bag and it belongs to Paul Kelly, Terrance Hill and Luis Salazar. They are not to be found anywhere. They were all single and that makes them the ideal victims. They all visited the anti depressant trials; and the trials are legit. Danny believes that this could be some sort of an experiment and that Dracul got the information of these guys from Tanner, as they were ready to go through drug trials. So they need to find out where the experiment is being conducted.
Just then Ho tells them that Tanner was in great financial difficulty; but two months ago he got a wire transfer from CF&Q. Callen recognizes the company as one of Dracul’s holdings. So, Tanner keeps half of the money and the other half he spends on buying medical equipments, which was sent to a warehouse in an island, which is called the Quarantined Island. They reach the island and find that there are cameras all over. Just then a car drives out and Callen sees Dracul in that car. They chase the car but in the end they only find the driver. They go back to the ware house. They find Luis and Paul dead in their beds. They too were infected by small pox. But it isn’t the small pox that killed them; Dracul shot them in their heads.
Max arrives at the scene with the CDC team. He tells them that the equipments are very sophisticated and that someone with acute scientific knowledge is involved. They also find tapes that have documented the progress of the disease. The doctor going through the tapes tells Kono that normally the incubation period of the virus is 16-28 days; but with this version of the virus, it is just three days. This means that anyone who comes in contact with this virus will be dead in 3 days. The doctor tells her that the voice that narrates never shows his face on the camera. She says that she knows the voice, but cant place him. Meanwhile, Ho and Danny go and visit Dracul’s driver at the hospital.
Danny threatens to inject the samples that they found in the ware house. He wants to know about Dracul. But the driver does not answer. But then when he sees that Danny has actually injected the liquid in his drip, he begins to crack. He tells them that Dracul has taken 9 vials with him and the sale is happening today at the International market. But then he also tells them that when Dracul arrived to pick up the vials, the guys were found dead, shot in the head. The doctor was missing but he does not know his name. Danny tells him that the drug that he injected in his drip is vitamin B 12. It aids in healing. Five o and NCIS are at the International market. Kono is keeping a watch from a distance. Kono tells Danny and Sam that the Chechens are closer to them. And Callen goes to get Dracul.
But Ho notices that Dracul isn’t carrying anything. Hana and Danny get the Check ins and find a bag full of money. Hana tells the team that the buy is still in play. Dracul’s bodyguard hands him a case. The vials must be in it. But Dracul notices Callen standing at a distance. He fires the gun in the air and the people in the market start running. Callen and Ho go in. But they manage to lose sight of Dracul. But Kono tells them that they split up and the bodyguard is next to the fruit vendors. Callen also spots Dracul. The bodyguard holds a girl hostage and tries to escape. But Kono shoots him. Callen is still chasing Dracul and he gets him. They have an argument and Callen shoots him. Callen gets the case of vials. Next, both the teams are enjoying the shrimps at Kamekona’s.
Just then Kono calls Danny and tells him that the doctor from CDC told her that the vials they recovered from Dracul, did not contain small pox and that the virus is still out there. Kono thinks that the doctor switched the vials. The doctor’s name is Gerard Perman. It seems that the doctor double crossed the guys he was working for. Kono tells the team that Perman is leaving for LA. Danny asks her to send him Perman’s picture. They arrive at the airport. But the guy they find there isn’t Perman. The guy tells them that Perman gave him $500 to switch flights and that he had some sob story about his girlfriend he is traveling with. Hana calls his colleague in LA and asks him to detain a passenger traveling under the name Benjamin Gallagher. Hana tells the team that they have a problem; flight no. 792 landed in LA five minutes ago. The episode ends.