The episode begins at a strip club, where few friends are celebrating their friend’s birthday. A lap dancer arrives and takes Joshua, the birthday boy, for a special treat. As soon as they enter the room, Joshua feels a little unwell. He passes out and the girl goes to get his friends. The friends arrive and see that Joshua is frothing and having seizures. They try to retrieve him. At that moment, another officer falls on the ground. At the office, Kensi has lost her tax return form and it needs to be submitted next week. She is shocked to learn that the rest of them have already submitted it. Eric arrives, announcing the latest case.
In OPS, they watch the footage from the strip club. Eric tells them that the dead guy is Lt. Joshua Gordon, a Navy pilot. The other officer who passed out is Naval Flight Officer Randall Baker and they also have a dead dancer. Eric and Nell tell them that it is cyanide poisoning, and that Officer Baker will soon be released from the hospital. The people who were poisoned weren’t drinking any alcohol; only water. Eric tells them that the Jihadist group is taking credit for this attack on the internet. Sam reads the post and tells the group that the message is full of grammatical errors. He feels that the person who wrote this doesn’t seem to know Arabic that well. Hetty thinks that that someone is trying to point fingers to deflect attention. Kensi and Deeks go to the bikini bar for investigation. They meet Detective Lopez and Lopez shows them that bottle of water that is poisoned.
He says that the water was changed by the janitor, Zaki Faheem. They have found the cap of the bottle and it looks like someone injected poison in advance. They are looking for Faheem. Deeks says that he wants to review last night’s footage. Callen and Sam are talking to Baker. They ask him about Joshua and if he had any enemies. Baker tells them that Joshua was a good man and it was not in his nature to make enemies. He says that he raised his voice only once on a guy named Fryman. Fryman is no longer in the service and was dishonorably discharged. Sam and Callen notice that Baker’s hands are shaking and Baker explains that this is the side effects of cyanide and it should get better with time. Kensi and Deeks find a syringe in the dumpster behind the bar.
They inform Eric and Nell. Nell tells Kensi that they have located Faheem’s cousin. She also tells her that 200 pounds of cyanide has gone missing from a silver coating factory. Sam and Callen go to meet Dominic Fryman. Dominic tells them that he never got along with anyone in the Navy and also he wanted to be home with his son. They ask him about Joshua. He tells them that Joshua had no family, no girlfriend and he never even dated anyone. He says that Joshua had a lot of secrets. Elsewhere, Kensi and Deeks manage to arrest Faheem and bring him to the interrogation room. Faheem tells them that he did not tamper with the water. He says that he heard about the dead guy and was sure that they would suspect him. That is why he called in sick.
Kensi and Deeks learn that Faheem is a well educated man and he works at the bar for money. They tell him that they will go through every email, text and phone call made by him. He tells them that a man with a beer belly kept coming for two nights in a row, asking if there were any job openings. Deeks wants him to identify this man from the security footage. Callen and Sam go to the silver coating factory and the woman at the factory tells them that they had ordered for five barrels of cyanide and there are just four. They check the remaining barrels and find out that they contain salt and not cyanide. This means that 1000 pounds of cyanide has gone missing, enough to kill 4 million people. Sam and Callen arrive at the ops and Hetty turns on the news channel.
It seems that three heart attacks have been reported in the past five minutes. Callen thinks that the cyanide could be in the city’s drinking water. Later, Eric tells the team that the COD in the three cases is cyanide poisoning. There was only one house in that block that gets bottled drinking water. Sam thinks that this was a local attack. Callen tells Kensi and Deeks to check the water supply in the neighborhood. He tells Eric to pull any recent rentals or vacant house in the same neighborhood. Kensi poses as an ambassador from the water supply department and tells the people that she can offer them tips on reducing their water bills. She says that she will need to check their faucet settings and supply pipes. They agree.
Deeks poses as a water sewage worker. The owner of the house, an old man named Eugene, tells Kensi that she should not go to the next house. He says that they shoot porn films and it will not be safe for her. At the ops, Nell receives a message from Kensi saying that she stumbled upon an adult film shoot. Eric tells her that Chanceworth is an epicenter of that industry. Eric tells Callen that he got a hit on a vacant house a block away from the area of the poisonings. Callen tells him to check on it. Kensi goes to the vacant house and sees a machine connected to the faucet. She tells Deeks to come to the house. At the ops, Eric tells Callen about a group called DNA (Designing New America), which aims at making America a better place for the children to grow up.
They want to get rid of child molesters, drug dealer, violent felons, etc. Callen tells them that it is obvious that they have a grudge against strip clubs. Nell tells them that they are coming up with protest at a lot of events like, political speeches, federal buildings, military funerals etc. Nell also tells Callen that the group wants the Defense to redirect their funds for education instead of war. At the house, Deeks and Kensi confirm that the pump they found was used to pump cyanide into the water system. Next, Sam walks up to a group of protesters at a military funeral. Callen, who is posing as a protestor, gets into a fight with Sam. The group leader is impressed with Callen’s conviction and tells him that he should join their group.
The leader’s name is Lawrence De Vries. Eric runs a facial recognition and finds out that Lawrence is a member of the DNA. Lawrence wants Callen to wear a blindfold while he drives him to the place where they function from. Sam is keeping a close watch on Lawrence. Nell tells Kensi that the vacant house had a plumbing visit and there was some equipment that was taken inside the house, but never came out. The van that transported the equipment was from a rental company. Kensi and Deeks go to check the car rental company. There they find Alex, Dominic’s son. Alex tells them that the company belongs to his uncle. The uncle tells them that he cargo van was rented by a Mexican guy.
They check the copy of the driver’s license and learn that it was Faheem. They go to Faheem’s house. Elsewhere, Lawrence arrives at his secret club house with Callen. Eric and Nell tell Kensi and Deeks that Faheem does not even have a proper license. They send them a traffic camera footage, in which they see that the guy they met at the rental company was the one driving the van. They decide to go back to the rental company. At the club house, Callen learns that he has been played. Lawrence arrives with Dominic Fryman and the guy from the rental company. Dominic is the leader of the DNA group. He tells Callen that he is trying to change America into a better place for their children.
Dominic gives Callen two options; either they shoot him to death or he drinks the cyanide. Callen tells him that he is not setting a good example for his son by doing this. Callen decides to drink the cyanide and they lock him up in a room. Eric and Nell manage to trace Callen’s location and Sam goes to the warehouse to search for Callen. Sam finds Callen and also sees a syringe lying next to him. It looks like he took an antidote. He is glad to see that Callen is fine. Later, at the ops, the team gears up to find Dominic and his team. Callen is not too stable because of the poison, but he insists on going with the team. Nell tells about an unauthorized repair work at the city’s main access points. Next, the team arrives at the site.
A gun fight ensues and Dominic loses all his men. He refuses to surrender. He ingests a bit of the cyanide and falls on to the ground. Callen tells them that they need to find the cyanide. He finds Alex sitting next to the equipment, ready to pull the valve. Callen convinces him to back off. Case closed. The next day, Hetty pulls a prank on Deeks. Callen arrives to meet Alex and they play a game of catch. The episode ends.