The scene opens in Kahala, O’Ahu. The Honolulu Police and Five-O arrive at a home where Steve says that Wo Fat is inside. He tells Agent Kaye that she is not a field agent and won’t have anyone dead. He handcuffs her to the police car door. They approach the front door and they open it a little bit. However, it is rigged and a bomb explodes and blasts Steve’s team back. Steve goes inside the house and is told that Wo Fat is still in the house. Meanwhile, Katy grabs a baton and breaks the door handle of the patrol car and gets in. Steve is told that Wo Fat ran upstairs. However, when Steve gets to him, it is not Wo Fat, but Sang Min. Shocked, Steve hesitates and Sang Min runs off and gets away from Steve. He runs into the street and hits Sang Min with the patrol car. Danny runs after him into a house. He finds a man dead inside. He checks the man’s pulse and verifies that he is dead.
Outside, Steve approaches the house, but has to dive out of the way when Sang Min almost runs him over. Steve tells the team that Sang Min was expecting Wo Fat and that the bomb want meant for him and not them. Suddenly Danny comes out coughing and says that something isn’t right. They call the ambulance and Danny tells that there is a body, but no pulse. Agent Kaye says that it might be biological and they need to get Danny to the hospital right now. They rush him to the hospital while a bio-hazard team tests for chemicals. Agent Kaye moves her radiation counter on the milk and it spikes. She packs it and says that it was the Nerve Agent, Serine. She says that she worked with the CIA on it. Danny was exposed when he checked the victim. Kaye calls Steve to get Danny on a medicine. Later, the team arrives and Steve says that Danny is responding to the medication. Chin Ho says that Danny has Grace this weekend. Steve says that they need to drop the search for Sang Min and get to the bottom line. Kaye says that she will call her contact at the CIA.
Steve goes to Grace’s school when Sang Min calls him. He says that he ruined his chance to kill Wo Fat. Steve says that he is not making a deal with him. Steve tells Grace that Danny is in the hospital and says that he is going to be alright. Back at headquarters, none of the samples are coming up with Serine in them. Chin Ho comes in with an ID on the victim. He ways Amoka Mulitalo and he was really in the home of Jeff and Sheila Fallon, a couple from California who uses the home as a vacation home. Chin Ho talks to Amoka’s daughter and she tells him that Amoka suffered from a disease and normally the police find him in a shelter. Kaye and Kono talk to the Fallon’s and say that Gabriel, their caretaker, stocked the fridge because they were going to go to Hawaii. However, they fired him for writing his own checks for himself. She calls Steve and tells him that they feel that the caretaker did it and Steve says that he has to go. He leads Grace inside to see Danny. He says that he is alright and will recover. She gives him a picture of him and her and he says that he will put it on his fridge. Rachel calls Grace and she says that Danny is in the hospital and Danny tells Rachel that he is fine.
Chin Ho and Kono go to a café and see Gabriel run away from them. Kono catches him and they take him down to the station. He says that he has a sick son and that is why he was stealing from the Fallons. He says that he had intentions to put the money back. He says that he didn’t try to kill anyone. However, he recognizes Amoka. He says that he told him about the rock. Kono goes back to find “the rock”. It is a spare key. Chin Ho tells Kaye and Steve that Amoka used to stay there so that he didn’t have to stay at the shelter. Steve believes that Gabriel didn’t kill Amoka. Kono comes in and says that she pulled a fresh print off the key. It belongs to Elliot Connor, CEO of the Fallon Corporation and Jeff’s brother-in-law. Chin Ho gets a call from IA and says that he already gave them his statement and tells Kono that he borrowed the money to give to IA. Kono says that all IA has to do is run the serial numbers of the bills. He says that they went missing. However, Kono tells that he needs to end this now. Steve and Kaye visit Elliot Connor and he says that there is no problem with Jeff and Steve tells that he knows about the affair that he is having with someone to cheat on Jeff’s sister. He asks to talk to the mistress and he says that it is his secretary, Chloe.
At the hospital, Kamekona comes in with fried chicken and says that they need some food. Danny asks him if he can find Sang Min and says that he will. Back at the station, Kono says that the Serine that was used was traced back to a Chechnya Group. The leader is Mikhail Yursky. He flew into Hawaii using a fake passport. They bust into Yursky’s hotel, but he is not there. Kono tells that there is a fresh hit and Yursky’s card is being used. Kono hacks into the ATM and stalls. Yursky sees Steve’s car and drives off. Eventually, they catch up and Yursky climbs over a fence, but than dies. He poisoned himself. They open the trunk and find a bunch of canisters. Rachel gets to the hospital and Danny says that she didn’t have to come and she says that she did. At the office, Chin Ho tells that the canisters are empty. Kono tells that IA is there and the officer says that IA wants to give back his money and says that he knows that his uncle stole from the police department and he is going to have to answer to that. Steve asks where he got the money and Chin Ho tells that he signed the deed to his house to Marcum. Steve says that he doesn’t have to explain anything to him and says that he needs to give it back.
Kaye tells that the canister that was used is Fallon’s Corporation. Steve and Chin Ho go into Elliot Connor’s office and ask if he talked to Yursky and he says that he was on the big island. He says that his secretary took the call. Chin Ho and Steve go to the parking garage and Steve almost gets run over. Steve stops her by shooting out her tires. She tells that Yursky offered her $20,000 for the canisters. She took the money and also asked him to plant the Serine in the milk at the Fallon’s so that she could kill so that she could have Elliot take over the company. Steve goes to the hospital to find Rachel lying on Danny sleeping. He tells him to be quiet and laughs. The next day, Steve gets a service medal that belonged to a Japanese pilot that bombed Perl Harbor. Kaye asks why it was in his father’s toolbox and Steve says that he doesn’t know. Danny gets back and says goodbye to Grace. Rachel says that she is grateful to come home and says that Stan and her are trying to save their marriage, but she doesn’t know if there is anything to save. They hug and he says goodbye. He gets into the station and he hugs Kaye for saving his life. Steve asks how long has he and Rachel been together and asks if he was ever going to tell him. Suddenly Sang Min comes in and says that he needs protection and says that Wo Fat will stop at nothing to kill him and then told him that he is coming for Steve next.