A woman in seen in flashbacks being thrown on the ground and beaten she screams as she is thrown against the wall. Her unseen attacker covers her mouth and holds a knife up to her face. On Ford Island, a man is running down the street with sirens in the background. A cop car blocks his path and he finds himself suddenly surrounded. He jumps over another car and climbs a fence, dropping to the other side, he runs down the street towards a battle ship. On the ship, an elderly man is giving a tour of the battleship, the U.S. Missouri. He asks them what they know about this ship and a girl raises her hand and says the ship was where the Japanese surrendered to the Allied Powers in WWII. Out on the street, police are closing in on the running guy, who is getting closer to the ship. The tour guide is telling his group that "She" was decommissioned in 1992 for a peaceful retirement here at Pearl Harbor. The man is caught near the gangplank of the Missouri and puts his hands up. As he appears to be surrounded, he grabs the police officers gun. He grabs a woman who is about to get on the ship and fires the gun in the air. Another officer tells him to drop his weapon and he shouts he didn't do it. As he drags the woman on the ship, he shouts again shouts, "I didn't kill my wife".
Outside the Missouri, Laura Hill, the governor's new public safety liaison meets Steve and Danny. She tells them the suspect on board, Graham Wilson, is a heavily decorated navy SEAL, from SEAL team 5 and is holed up inside with an unknown number of hostages. Danny asks if there has been any contact and Laura tells them that Wilson told the negotiators he'd start killing hostages if anyone tried to move in on him. Steve asks about the demands and Laura says there was just one; find his wife's killer in four hours. She explains Noreen Wilson was killed earlier this morning and Graham is the only suspect. She states that he was found at the crime scene holding the murder weapon and when confronted, he ran. Laura tells them her only concern is getting the hostages off the ship. Steve asks about S.W.A.T. and Laura explains the governor thinks his SEAL background makes him the better person to handle this situation. Steve tells his team that he will be going in alone. Danny replies, "Well, that's just stupid." Steve tells him that Graham's a SEAL, he's been trained and now he has the high ground. If you sent S.W.A.T in blind, they will, at least, get multiple hostages killed. If he didn't kill his wife, he deserves a conversation before they go in guns blazing. If he did, Steve will take him down. Steve tells Laura that if they want his help, they will need to do it my way.
Danny asks Steve, "Okay, uh, let's say I am you, and you are the bad guy here. I would know that all the ways onto the ship are visible somehow, so how would you outsmart yourself and get yourself onto that ship, without yourself seeing... yourself?" Steve wonders if that was an actual question or if Danny just threw words together to see if they made sense. Danny asks how he's going to get on the ship without Graham seeing him. Steve says that Graham's expecting someone from the land, not the water, stating he is going to go for a swim. Danny questions Steve if he is serious watching as Steve takes off his shirt. He explains to Danny that he has done this before. Danny asks, "You mean you've snuck onto a floating museum to rescue a bunch of tourists being held captive by a man who is accused of killing his wife?" Steve backpedals, not this literally, but he doesn't see any other way, as they only have four hours. He tells Danny to look into the murder case while he gains Graham's trust in order to get everyone out safe, including Graham. Danny asks what happens when he investigates the case and finds out he killed his wife and Steve responds that they will at least know the situation. Chin & Kono join them and he reports that the HPD responded to neighbors calling because they heard screaming coming from inside of Graham's house. He continues stating that when HPD arrived, they found Graham holding with the murder weapon and then he ran. Kono adds they also found his seven-year-old daughter hiding under the couch. She hasn't talked since Child Welfare Services took her into custody. Danny suggests that she may have seen something. Kono tells them that she was planning on going to go see her, since they'd probably ask her to anyway because she is the woman. Danny corrects her stating it is not because she's a woman, but a rookie noting it is worse. Steve tells them that he will have his phone, clarifying that the will call them. Kono states that she bets he uses that line before, as she walks away. Steve ignores the comments and tells Danny & Chin that he will contact them once he's in a secure location. Chin notes that he probably used that one, too. As Steve heads towards the water, Danny yells, "Good luck Aquaman."
Steve drops his shoes into a sack, which he secures to his back then jumps into the water. He swims past fish and turtles until he comes up on the side of the ship and starts climbing up the side. Once he gets to the top, he pulls out his gun at the ready, but no one is up there. He pulls out his sack and digs out his shoes, shirt and a map of the ship. Somewhere inside the ship, he moves slowly down a hall, turning a corner, he runs into the tour guide, who states, "It's about time back-up arrived". He introduces himself as Ed McKay and tells Steve during his tour there were shots, then chaos with people running everywhere. He was able to get most of his tour out, but some fell behind, relaying that Graham has seven people hostage. He tells Steve that he is holding the hostages in the wardroom and Steve gets out his map. He asks Ed if there is a safe place for him to hide, but Ed tells Steve he's going with him, stating that these are "My people". He walks the ship back and forth five times a day and no one knows it better than he does. Steve agrees to take him but tells Ed that he has to do what he's told. Ed salutes him and Steve tells him to stay out of sight no matter what.
At Child Welfare Services, a sad little girl hugs a teddy bear, as Kono asks a nearby worker who will take care of Lily. The worker says Graham's sister is flying in from Oklahoma and the worker hasn't found anyone on her mother's side who is local. Kono asks if she's said anything about her mother's murder but the worker says she hasn't said anything. Kono approaches Lily and introduces herself. She continues by saying that she bets Lily's been asked a lot of questions. She tells her that she's not going to ask her any questions right now. She then tells Lily that she going to get some "shave ice" and asks Lily if she would like to come along. A small of a smile appears on Lily's face.
In the ship, Ed asks Steve if he thinks Graham killed his wife and Steve responds, "He's going to a lot of trouble to say he didn't". Steve hears Graham and turning a corner, gets a visual on him and the hostages. He sees that Graham is pacing around, looking outside seeing S.W.A.T. surrounding the ship. One of the female hostages starts to speak, but Graham says no talking. She continues explaining that she is hypoglycemic and she sent her husband to get her a snack. If she doesn't get something to eat, she'll pass out. Graham asks the other hostages if they have any food. A man hands a packet of peanuts. The woman thanks him and eats them. Steve watches as the Graham tells them not to talk anymore and promises to hurt them if they do.
Chin and Danny are looking around the Wilson's home on Ford Island. They fine blood everywhere and upturned furniture leading them to believe it was "a hell of a struggle". Danny voices that the crime scene isn't making sense, stating that Graham is a Navy SEAL & his wife was a small woman. He continues stating that it would have been an easy kill and Chin wonders why it is so sloppy. Danny suggest that it could be a result of the love and hate relationship, two sides of the same coin. Danny lays out the possible scenario a marital spat escalates, Graham snaps, going from heads to tails. First, he just wants to make her suffer a little bit, then the wife ends up dead. Chin asks Danny how long he was married and Danny states it is only a theory. Danny rifles through a desk when there is one drawer that's tough to open. Chin helps him pull it out and they find a small journal stuffed under it. The journal is written in Russian which Danny recognizes from a case he worked in Jersey. Chin says there's nothing in Graham's file about language training. There is also a key in the journal. Danny says they should get it translated as it could've been Noreen's and find the safe deposit box the key belongs to. Danny 's phone rings it is Steve telling him he has found Graham's and that he has seven hostages Steve comments that Graham seems pretty erratic and Danny questions as opposed to most people who take hostages are calm and composed? Steve explains that a man with Graham's training, the situation shouldn't bother him yet he is paranoid and unstable. Steve wants them to check if he has been treated psychiatrically. Chin goes upstairs to see if there are any medications. Danny tells him about the journal and key and Steve notes he is making progress. Danny asks Steve if he misses him, who responds that he wishes he were here, but he doesn't swim. Danny tells him he can swim, he just chooses not to. Ed asks Steve if he's talking to his wife and Steve clarifies that it is his partner. Chin comes down the stairs, having found clonazepam, lithium and an anti-psychotic, commonly used to treat posttraumatic stress disorder. Chin continues stating that all prescriptions were written by Dr. Klesko and the bottles were filled three weeks ago but almost full. Danny ponders about what would happen if he stops taking his meds. Graham begins yelling at the hostages that they don't want to make him angry. Steve says he just found out noting that the longer this goes on, the worse it's going to get. Graham hears Ed hit the wall and yells out into the hall to see who's out there. Ed and Steve duck back behind the corner. Steve grabs Ed's hat and tells him to get out of here. He comes out from behind the corner pretending to be a tourist, Graham pats him down, then puts him with the other hostages. The hypoglycemic woman is sweating and panting prompting Steve to try to help her, but Graham points his gun at him and orders him to be quiet.
At the Naval Health Clinic in Malakapa, Danny asks Dr. Klesko why she was treating Graham. Dr. Klesko tells them his team walked into an ambush in Iran and the crossfire ended up killing a group of children. The trauma caused Graham a huge psychological toll which manifests in mood swings and some violent behaviors. She tells them that the MP's had to be called to his house for domestic disturbance. She says they were making progress with his posttraumatic stress disorder until he became convinced the drugs were affecting his judgment and started skipping doses. He started experiencing blackouts which is where he may slip into a dissociative fugue state when agitated and could become enraged or violent. When it's over, he'd have no recollection of what happened. Chin says it's possible Graham killed his wife without realizing it. Danny says it's more than possible.
In the ship, as the man next to Steve gets up, Steve whispers to him not to do it only he doesn't listen and tries to attack Graham. Graham takes him down leaving the man on the floor, bleeding. During the fight, a knife falls on the floor that Steve pockets. He stands up going towards the injured man and Graham demands to know who he is. Steve tells him he is with the 5-0 unit, but he used to be a SEAL like Graham. He tells Graham he came in by himself so Graham could tell him what happened. For his service he thought he deserved at least that much. Graham puts his gun down and says he didn't kill his wife. Steve says he believes him and states that his team is investigating the case. Graham puts his gun back up and demands to know where the knife is. Steve reasons with him that he has a gun and is in control. He says he has to do the right thing for his daughter. Graham demands where she is and Steve gives him his word that she is safe. He tries to get Graham to release the hostages but Graham refuses. He convinces Graham to allow him to help the injured man. Graham has the hostages empty their purses and pockets and Steve picks up supplies. Steve tells Graham that he hurt the man but luckily didn't kill him. Graham says, "I know" pointing out that if he wanted to kill him, he'd be dead.
At the shave ice stand, Kamekona brings Kono and Lily two shave ice's. Kono and Lily start eating without talking. Kono asks if it's good and Lily nods. Kono says her favorite's grape because it makes her tongue purple, sticking out her tongue and Lily laughs. She notices Lily's only eating one of the two flavors of hers and Lily says, "Daddy eats that part".
In the ship, while helping the injured man, Steve tells Graham a story from when he was a SEAL. Graham recognizes the name of the chief as he had him too. Steve asks where he met Noreen and Graham said Germany six and a half years ago. He was traveling on leave through Europe and she was working in an all-ranks place. She had just immigrated there with her daughter and they were married three months later. Steve tells him that he knows she is from Russia. Graham said she changed her name from Irina to Noreen before they came to the States, to put her past behind her. Steve asks if Lily was from a previous marriage and Graham says her father died before she was born. He says he can't imagine what Lilly is going through. Steve asks what happened that morning and Graham says they fought. He doesn't even remember about what and continues by saying that he knows he's difficult to live with since he's been back. He states that sometimes Noreen would say she was scared of him and that he wasn't the same guy she married. But he was getting better, his doctor told him to take two laps around the block when he got worked up so that's what he did. When he came back, Noreen was in the middle of the living room and he ran to her, trying to resuscitate her when the cops showed up. He states he got scared and ran. He swears he didn't hurt Noreen and tells Steve that it means everything for Lily to know he didn't do this to her mother. Graham looks at Steve and tells him to get back, just as Steve tries to reach for the gun who. Steve reports the injured man needs a CAT scan and needs to get off the ship. Steve tells Graham to prove to him that he is a good man by letting the injured man leaves. Graham agrees and they watch as he gets up and walks out the door. Graham then tells everyone else to get on their feet stating that they are moving out. He states, all except for Stave who he puts in a dark room and threads a ladle on a chain through the door. Steve turns the light on and finds he is locked in a bathroom.
Steve calls Danny, who is at the office and they discuss that he is locked in the head. Danny exclaims, "You're in a bathroom? I could've got locked in a bathroom." Danny wants to call S.W.A.T, but Steve tells him not to, that he will find a way out of there. Danny states that they sent the journal off to Catherine to get interpreted. He tells Steve Graham could have killed his wife without knowing it, but Steve says it doesn't make sense. Danny points out he fled the crime scene with the murder weapon and is still the prime suspect. Steve says Graham identified him as a threat and didn't do anything. Steve says he promised they would investigate which Danny points out he's doing, but to broaden the search he needs something else. Steve tells him about Noreen's first identity, Irina and Danny tells him he got a match on the key to a safe deposit box at the First Hawaiian Bank. In the background, Danny hears banging and asks what it is. Steve says he will call him back and hides behind the door. It turns out to Ed with Steve's stuff. Steve asks how he got past Graham without being seen and Ed says he knows things about the ship that aren't on a map. Steve recalls he told Ed to stay there, and Ed says he's an old man and he doesn't always hear so good.
Outside, the injured man is coming outside, with his hands up yelling, "Don't shoot, I'm a hostage". Laura gets a call from Graham who says she gets the injured man but he keeps Steve and everybody else until they find who killed Noreen. Laura wants to talk to Steve, but Graham tells her all she needs to know is he's still alive. He tells her that he is watching her and they have less than two hours before the next hostage comes out in a body bag. He warms her against pulling any more stunts.
Ed is surprised Steve had Graham's knife and didn't use it. Steve says there's a way to do it where nobody has to die and it's evidence. He shows Ed the dried blood on the knife and says there's a fingerprint in there that was put on the time of the murder. Steve using a compact he got out of one of the women's purses, dusts the handle of the knife, revealing a fingerprint. He takes a picture of the print and sends it off, stating 'This could be what clears him". Ed remarks that Steve really believes Graham's innocent. Steve says his team's motto is "Leave no man behind". Steve says Graham would want a good view of the gangplank, so he thinks he took the hostages to the pilothouse. Ed tells him he knows a shortcut. As they climb through an area, Ed tells him he knew the name Steve McGarrett and asks if Steve's grandfather was in the navy. Steve says he was stationed at Pearl and Ed remarks he was a tough son-of-a-gun. Steve stops him and asks he served with his grandfather. Ed says they were stationed at Arizona, but it wasn't luck, he wasn't on board that day. He lied about his age to enlist and he was sixteen and they found out but the officers liked him so they kept him around as a runner. He was running messages back and forth between the ship and Fort Shafter on December 7th, 1941. He could see the explosions but he couldn't do anything for the men giving their lives. Everyday he walks past the Arizona memorial and is reminded of their sacrifice. He tells Steve the man he is named after was a real hero. He should be very proud and Steve confirms that he is.
At the picnic table, Lily is drawing a picture of her and her parents. Kono draws a picture of herself surfing and tells Lily that's what she was doing this morning. She asks Lily to draw what she was doing and Lily draws a picture of her hiding under the couch. She tells Kono she hides there when there's too much yelling. She draws a pair of shoes but says they are not her dad's shoes. Kono assures her nothing will happen to her and Lily says it is the man who yelled at her mom. Kono asks if her dad was there and Lily shakes her head. Kono tells her it's really important for her to know who the man was and what they were saying. Lily says she can't talk funny like they did but they yelled a lot, then her mom got hurt. Kono asks Lily if she wants to see where she works when Lily gets afraid as she watches a man coming towards them. As Kono goes towards the man, Lily runs away. A SUV drives up, grabs Lily and throws her into the back. Kono chases them on foot, but they drive away.
Kono tells Chin about the kidnapping but Chin assures her there was nothing she could have done as they were targeting Lily. Danny is on the phone with Steve and tells him what happened. He says the fingerprints on the knife don not belong to Graham or Noreen. Steve says they have abductors, a witness that puts another man in the house at the time of Noreen's murder and fingerprints that are not Graham's. He says it looks like Graham didn't do it, but Danny says it's not over yet. Steve tells Danny that he needs to diffuse this hostage situation and Danny reminds him that under no circumstances to tell Graham about Lily. Steve thinks he should know, but Danny says he shouldn't know, explaining that from a father's perspective the last thing you want to hear is something happened to your kid and on top of his already erratic state it would only get worse. Danny cautions Steve not to go soft on Graham because if he did kill his wife, Steve needs to take him out. Steve says it won't come to that and hangs up. Steve and Ed are now on a deck above where Graham and the hostages are. They go down to another side of the deck. Steve calls out to Graham and tells him they need to talk. Steve tells him he believes him and soon his team will have proof that he did not kill Noreen. Graham wants to know how but Steve tells him to let the hostages go first. Graham thinks he's lying and shoots out the window. Steve tells Ed this has gone on too long, stating, "It ends now".
At headquarters, Chin reports that they found Noreen's passport and she was born in Irina Tatasova in St. Petersburg, Russia in 1979. Catherine sent over the translated journal, which Kono reads, noting that Noreen was married to Yegor Chubais, the VP of the Donvaga Bank in Switzerland. She continues stating that it sounded pretty brutal, multiple accounts of domestic violence. Chin brings up a picture and says he filed a report saying his wife and newborn child went missing on a trip abroad. Kono recognizes him as the man who kidnapped Lily. Chin says he came to Hawaii three days ago and has a plane to Moscow that leaves in an hour. Danny realizes she came to the United States to get away from him and when he found her & she wouldn't come with him, he killed the mother of his child. Danny says they can't let him get on that plane.
Steve puts on his gas mask and throws a gas bomb through the broken out window into the room where the hostages are. Ed opens the door tells the hostages to follow him out. Steve comes through ht the window looking for Graham. Steve opens a door and then feels a gun on the back of his neck. Graham orders him not to move and takes his gun.
Danny, Chin and Kono drive to the airport while trying to call Steve. Graham pushes Steve through a door when his phone goes off. Steve tells him it could be his team with the proof to prove his innocence. He orders Steve to put it on speaker and Steve tells Danny that he is there with Graham. Danny tells him they are their way to get the man who killed Noreen, Lily's father. Graham says that is impossible because he's dead, but Steve suggests that maybe Noreen lied to protect him from a life she was ashamed of. Graham states that it is a lie and throws Steve's phone in the ocean. Graham orders Steve onto his knees and to put his hands on his head. Graham stands behind him, ready to shoot. Police are helping hostages outside when Laura tries to call Steve. She gets his voicemail and tells the sergeant to deploy his men.
Danny speeds the car into the airport right as the plane is about to take off. He drives the car through a gate and stops on the runway right in front of the plane. Kono motions to the pilot to turn off the engines and the men inside disembark the plane. Lily's father and his men are arrested by Chin and Kono runs up and hugs Lily and tells her she is safe.
Steve tells Graham they can still work it out. Graham says we argued and he took two laps around the block, while Steve says they got the guy. Graham laments if he didn't take the walk, while he's talking, S.W.A.T. men come up the ship. Graham wonders if he killed her but Steve tells him he didn't. Steve sees one of the S.W.A.T. persons aiming and orders them not to shoot. Graham reacts and shoots him first. Ed comes out of a doorway and is hit by a bullet. Graham is surrounded by S.W.A.T. men who order him to drop his gun and get on the ground. As they are about to shoot Steve tackles Graham onto the ground. He calls for a ceasefire as Graham is arrested. He runs back up to see if Ed's okay. Ed remarks that getting shot hurts and Steve asks what he was thinking. Ed answers "Leave no man behind." Steve smiles and says he is crazier than he thought.
As Graham is being escorted away, Steve sees the team with Lily. He convinces them to let Graham see his daughter without handcuffs. The cuffs are taken off and Graham looks at Steve, surprised. He walks down the gangplank as Kono points him out to Lily. She yells, "Daddy" running into his arms and asking if they can go home. He tells she is going to stay with Auntie Susan for a while as he is a little bit sick and he has to get better. He and Lily hug again as Steve walks past to rejoin the team.