In the bullpen, Tony is spring cleaning and finds a back scratcher, which he immediately begins to use. Abby enters and is upset about having a cavity and is on the way to her dentist. Gibbs enters and they take off for the crime scene. The victim is PFC Marco Riggs. His cell scanner is what the baby monitor picked up when he was trying to call 911 with it.

Ducky and Palmer arrive. They explain the traditional reasons for being unshod (Riggs is barefoot). The time of death appears to be 2 hours ago. They reveal two puncture marks on his neck. Palmer declares that Abby is going to love this. Abby comes out of the dentist office very happy and is met by the FBI. She is requested to come with them but can't tell her where.

At the bullpen we learn that Riggs was accused of stealing military equipment and selling it on the black market. He disappeared before he could be charged. He's been missing a week. Fornell has advised Gibbs that Abby has been picked up by FBI. He calls her while she is in the car. She advises there is a step-by-step guide for her lab. The punctures marks are from a stun gun and not a vampire bite. He suffered a stroke and took off his shoes because his feet felt like they were burning. Abby's replacement does not arrive until Monday. Tony and Tim get the job of handling the evidence in Abby's lab, while Ziva assists Gibbs in the field.

Abby is told she was "asked" to be there at the request of Dr. Philip Heller at Tarburst. Dr. Heller was working on a project that cannot be talked about, but Dr. Heller is no longer with the program. The lab is state-of-the-art. She is told by Dr. Jones that they do not know what he was working on. A patient, Robert King, walks into the lab and starts chatting Abby up. Nurse Dunstan hauls him off.

Tony tries to break into the only locked drawer in Abby's lab. Palmer, McGee and DiNozzo make a mess of Abby's lab in attempting to run identify the DNA found under Riggs' fingernails. Abby calls in that she needs a background run and warns Tony that screwdrivers leave marks on locked drawers.

Ziva and Gibbs are back at the crime scene. Ziva babbles on about how much she enjoys the silence without Tony's incessant babbling. They find cement, rope and other items in the trunk of Riggs' car. It appears Riggs was the intended criminal rather than the intended victim. Abby tells Dr. Jones that she is done. Dr. Heller was attempting to hijack DNA's pathways in order to target a specific strand of a person's DNA. She is irritated that Jones already knew that. She threatens to storm out but he tells her that all the patients are going to die if she does not help.

McGee gets the results of the background check on Dr. Heller that Abby requested. The realize he has disappeared because someone was trying to kill him. And Abby has just taken his place. Dr. Jones pisses off Gibbs, who is concerned for Abby. About a year ago, the company became involved in the medical study of Afghanistan veterans. They discovered a number were suffering from a fatigue and got a contact to research the Afghanistan War Syndrome. They don't know where Dr. Heller is. Gibbs wants Abby returned for her own safety, but Abby refuses to leave. King returns to Abby's lab. He and Abby play a game of chess. Abby and he save the research bunnies.

The team continues their search for Dr.Heller. The FBI have had a BOLO out on him for a week. He is a biologist, not an MD. He had a gambling addiction but does not spend more than he earns. Gibbs and DiNozzo go to check out Dr. Heller's wife. She is having a garage sale and is hostile about him. He said he was going out for a walk and never came back. She is pissed. They trace flowers bought on Dr. Heller's credit card and Dr. Heller ran when they tried to get inside. He was carrying a stun gun.

Under Gibbs' interrogation, Heller says he was accosted by Riggs when he was talking a walk. Riggs stuck a gun in Heller's face, so Heller stun gunned him. He thought it was a simple mugging, so he did not call the police. Gibbs states he is not telling the truth and he did not go home because Heller knew it was not a mugging but a hit, and they knew where he lived. Heller admits they are trying to kill him because he discovered the truth: the tests were compartmentalized, so it took him a while to figure out that he was building a weapon, not working on a cure for the sick people.

Abby shows up at King's room ready to play chess, only to find an intern on his cell phone ("I don't know where they all came from, but suddenly there were about a dozen rabbits in the hall.") It appears King is dead. She tells his room that she did it - she isolated the "never mind. You would find that so boring. It's not a cure but maybe some day...." And then you hear Tony yell "Found her!" Ziva and Dr. Heller arrive to state the lab is secure.

Back at NCIS, Abby is outraged (Abby's Rule # 1: Do not lie to Abby). Someone has already downloaded all of Abby's research. Jones is gone; an aide said he left in a hurry. They put out a BOLO and coordinate with local LEOs (law enforcement officers). Abby explains that she created an enzyme to target the G cells of the sick solider. He had Dr. Heller create an immunigen to kill off foreign matter. Together they can be used to target only the intended victim. "Heller made the bullet and I made the gun." He didn't build it to kill someone, he built it to sell it.

Abby's lab is a mess still, but she works away at her computer hacking into Nurse Dunstan's file as a hunch. She emails the file to Tony to send out a BOLO. She tells Gibbs she cannot find any sign that there ever was an Afghanistan War Syndrome. Someone in the lab was swapping out their diseased blood with health samples. Doctors had sick patients but normal test results, so they thought they had a war syndrome on their hands. Jones tricked the army into financial the project and Nurse Dunstan was on call every time there was a blood test.

Ziva calls that they found Nurse Dunstan's body. Down in autopsy we discover she was strangled. McGee advises Abby picked up a data fetch from Jones' smart phone; she got an airline and a flight number. Abby is outraged that Jones is left to sit: "Sit!?! He gets a chair!?!" Gibbs enters the interrogation room and Jones offers to make a deal to cooperate. He is surprised when Gibbs mentions a killing. He is not selling the research, he's running because he was embezzling the funds. Abby's success would mean a GOA audit and he would be found out. Abby bursts in and accuses him of falsifying medical records, like King's. He does not know King and he knows every patient in that hospital. Gibbs only response is "Find him."

We see King at a laptop typing a message that says "I have the package. Auction starts at noon." Gibbs and Abby confront him with Tony and Tim as backup. In response to his question "What did I do wrong?" he learns he was playing with the wrong forensic scientist: fingerprints and unencrypted emails got him.

McGee gets off the elevator and Tony is puzzled looking at Abby but not approaching her or her lab. They both had gotten an email from Gibbs to meet them down in the lab. It is not until they step into the lab and the door shuts and locks behind them that they realize Gibbs doesn't use email. Palmer greets them cheerfully from the floor, which he has been scrubbing clean. They each have cleaning buckets with supplies and their names on them. Abby just smiles at them and waves.