The scene opens with Castle and Martha in a bank. Martha is trying to get a loan to cover the damages to her theater, but the bank manager doesn’t want to give it to her. Castle suggests that he give her the money instead, but Martha says that she wants to get this on her own because she is a business woman. Castle calls Beckett up and tells her to tell him that she needs him for something. He watches the bank and sees two people enter the bank in scrubs and masks. He tells Beckett that he thinks that the bank is about to get robbed. Beckett tells Castle that he is over-analyzing it, but suddenly a man enters and tells everyone to get on the ground. Beckett tells Ryan and Esposito to call up SWAT for a bank robbery. She says that Castle is inside the bank. Castle tells Beckett what is happening and says that there are 3 bank robbers. However, another bank robber comes up behind and puts his gun to Castle’s head. Beckett talks to the man and he says that he’d rather make the front page. The cops arrive and the lead bank robber tells everyone to get comfortable.
Outside, Beckett goes inside the Team Leader’s van and meets with Commander Peterson. She says that her partner is in there and says that she talked to the lead man. She says that he was calm. Peterson tells Beckett to leave. Inside the bank, one of the robbers tells that if they move, they die. Castle reassures everyone that they will be alright. Beckett goes up to Esposito and Ryan and tells them that she has nothing. However, Peterson calls her back in and says that the lead man will only talk to Beckett. She gets on the phone and the man tells her that she can call him “Trapper John”. He says that if she lies or messes with him, he is going to kill hostages. He tells Beckett that he will start with her boyfriend, Castle. Peterson tells Beckett that they are going to have to wait because “Trapper John” is not an amateur. Back inside the bank, one of the hostages tells Castle that it is his fault because he called the police. However, the bank manager says that the robbers took from the bottom and it triggered a silent alarm. Castle sees that the robbers are going in the back for things when there is a case full of money. The bank manager says that there are safe deposit boxes. Castle pretends that he has to go to the bathroom and sees “Trapper John” emptying out a safe deposit box in back.
Outside, Esposito tells Beckett that the hostages don’t have a chance of survival in these situations. Castle gets back and tells the other hostages an update. One of the hostages gets up to use the bathroom too. Castle says that “Trapper John” took down a box on the far right and in the middle. The bank manager knows the number and says that it is Box 120. Castle asks for Martha’s watch and says that he has a plan. Beckett calls “Trapper John” and tells him to allow the pregnant hostage go and “Trapper John” says that he wants a bus ready to go that he can load the hostages on and then they have a jet waiting for them at the airport. They agree on it. Beckett sees a flashing light on the ceiling outside the bank and realizes that it is Mores Code. They break it and find that it is SDB120. After a little guesswork, they realize that it stands for Safe Deposit Box 120. One of the officers pulls it up and it belongs to Agnes and Gideon Fields. The hostage comes back from the bathroom and says that there are white bricks with wires in the robbers’ bags. He says that it might be C4 and says that he has a family to look out for. He says that his name is Sal Martino and that he has son named Conner. Castle tells him to keep thinking about him. Martha says that they don’t want anyone to know what is in that Safe Deposit Box.
Ryan and Esposito go to the Field’s residence and there is no one answering. Ryan says that the husband, Gideon, has been dead for a while, but that someone has been using the box with Agnes every month. Ryan says that he “hears” someone crying for help. They bust in and find Agnes dead. They call Beckett and tell her the update. Ryan finds out that Agnes’ place was bugged. Beckett sees Alexis and tells her that Castle and Martha are in the bank, but says that they are going to be alright. Inside the bank, Castle says that he has to alert Beckett about the C4. He tells one of the bank robbers that they shouldn’t allow a pregnant woman sit on the hard floor and offers to go to the chairs and get a pillow or something for her. She agrees to allow him. He stands up and Sal stands up too. Castle realizes that Sal is having a seizure and sees on his arm that he is epileptic. Outside, Beckett tells Alexis that they are doing their best and that they will be fine. She tells her that they better be. Alexis tries to call Ashley, but she gets a voicemail instead.
Beckett gets a call from “Trapper John” and he says that they have a hostage who had a seizure. He says that they are going to send in a paramedic and then have their bus there in 20 minutes. Beckett tells him that they are going to need more time, but “Trapper John” says for her to do it or he will start killing hostages. Beckett tells Peterson that she is going to go in as a paramedic to assess the situation. She goes in and Castle writes down “C4” on a bank receipt. They lift Sal on the gurney and she takes the paper and Saul out. She goes back outside and Alexis asks for an update. Beckett looks at the paper and tells her to stay back. Beckett talks to “Trapper John” again and tells him that the bus is on its way. He says that her time is up and shoots his gun at Castle. However, it was only a warning shot and tells her to get the bus to him now. She gets violent with him and tells “Trapper John” that if he kills Castle, she will walk in and put a bullet through his head. He thinks about it and then says calmly that she has 20 more minutes. Another bank robber gets a call and tells “Trapper Jack” that they are ready to go. Castle asks why they are robbing the bank and he says that because of the saying from a bank robber. Castle says that he knows about the C4 and the fact that they triggered off the alarm themselves. “Trapper John” laughs and tells everyone to get up and tells the other bank robbers that they have trained for this.
In the Command Center van, Beckett doesn’t get why he didn’t want anything in return and says that something isn’t right. Inside the bank, Castle tells Martha that he doesn’t like the customer care in the bank and would like changing banks. She apologizes for bringing him there, but he says that it is fine. Esposito and Ryan call Beckett and tell her that there is only a former son-in-law named Ron Brandt is still alive and that the daughter and grandson of Agnes and Gideon are dead. Beckett tells them to keep looking when suddenly there is an explosion from inside the bank. She walks out thinking that everyone is dead, but finds that all hostages are safe inside a vault cell. She goes up to Castle and says that she is happy that he is alive. Peterson says that the bank robbers are all dead. Beckett doesn’t understand it because C4 is stable and that it had to go off by someone else’s hand. Peterson says that there are body parts everywhere. They go outside and Alexis runs up and hugs Castle and Martha. She says thank you to Beckett. Ryan and Esposito show the picture of Ron Brandt. It is the hostage who said his name was Sal Martino. Beckett calls the hospital and finds out that he checked out against medical advice.
They get to the station and find out that Ron Brandt was married and had domestic charges. Castle says that he talked about his son Conner as if he was still alive. Ryan says that there were checks written to a church to St. Abigail’s Church. Beckett and Castle go to Father Sean McCaskey and tell him that they need to know where Tanya and Conner Brandt. He says that they’re dead, but when Castle tells him that Ron is on his way. He tells them that they are in Ithica. Ron gets to Tanya’s home and she has a bat. She tries to fight, but he is stronger. He goes in and gets Conner. Beckett tries to call and wait fort he police. Ron tells Tanya that he is going to go out and disappear. The police arrive and arrest Ron. Beckett gets off the phone and says that the police got him. Castle is impressed that he solved a murder as a hostage. She offers to get drinks at the “Old Haunt”, but Castle says that he has a better idea. He has her come with him to his house where Martha has prepared a feast. Castle goes in to find Alexis breaking up with Ashley. He asks if she is alright and she says that he needs to ask her tomorrow. Castle goes in the kitchen and tells Beckett that he has saved Beckett’s life 9 times and she has only saved his life 8 times. She doesn’t believe him and he reminisces on all the times. The episode ends.