Castle and Martha are trapped as armed bank robbers dressed in hospital scrubs and using names of TV doctors take hostages. Beckett was on the phone with Castle when the action started. The lead robber, who goes by Trapper John, will only talk to her. Looks like Beckett has gone from top homicide cop to instant hostage negotiator. Trapper John promises that if she messes with him, he'll kill Castle first.
Castle realizes this isn't an ordinary bank robbery. The hostage situation was planned so that the bad guys could have time to look through safe deposit boxes. If Castle can figure out who owns the box Trapper John is interested in, he may be able to figure out his plan. Speaking of plans, Trapper J wants a bus to take his crew and the hostages to the airport. He'll release a pregnant woman there, but everyone else will go along for the ride.
Using a reflection caused by Martha's bracelet, Castle is able to relay a Morse code message to Beckett outside regarding the safe deposit box. It belongs to a married couple named Agnes and Gideon Fields. They both access the box monthly. On the inside, a panicky hostage says he spotted some explosives in a robber's bag. Castle calms the guy down by promising that he'll figure out a way to save the day.
Ryan and Esposito discover that Agnes Gideon has been dead for at least a week. Her apartment had been professionally bugged. Back at the bank, panicky hostage guy has an epileptic seizure. Trapper John will let a paramedic help, but he pushes the delivery time on the bus from three hours to 20 minutes. Beckett dons an EMT uniform to tend to the sick man. She tells him that there are people out there who care about him and that's she'll get him out of there. Castle knows those words are really meant for him.
Castle slips Beckett a note about the explosives. The bus is stuck in traffic. There's no way it'll make it to the bank before the deadline. Trapper John promises he's going to kill Castle if the bus isn't there in one minute. Beckett assures this bad TV doc that if he pulls the trigger she'll personally walk in there to put a bullet through his skull. Just like that, Beckett has more time. Turns out she's a pretty good negotiator after all.
Even though they are on opposites sides of the bank doors, Castle and Beckett are completely in tune with their deductions. Like we said earlier, this is more than just a bank heist. The hostages are bound by the hands as the robbers prepare for their next move. Outside, Esposito calls Beckett to say that Agnes Gideon's only living relative is a former son-in-law named Ron Brandt. Then...
BOOM! An explosion rocks the inside of the bank. A look of sheer horror covers Beckett's face as she steps up to see the tragedy. The police storm inside to find all the hostages alive and well in the vault area. Beckett is relieved to see that Castle is safe, too. Outside, a worried Alexis has been trying to get her long distance boyfriend, Ashley, to comfort her on the phone. He was just too busy, so she was out there all alone. Not anymore. Alexis is overjoyed as Castle and Martha exit the bank and enter her emotional embrace.
An assortment of body parts lead the police to believe the robbers all died in the explosion. Castle doesn't buy it. These guys were too good. When Beckett sees a picture of Agnes Gideon's son-in-law, Ron Brandt, she realizes he's the hostage who had the seizure. The guy used his military contacts to orchestrate the entire operation. Then he blew the explosives early to kill off all the mercenaries he hired. One big question remains. What was in that safe deposit box?
Brandt abused his wife, Tanya, who faked her own death to escape from his clutches with their son. The safe deposit box was the only way Tanya could safely communicate with mom Agnes. Brandt now has all the information he needs to kidnap his son and kill his wife. They need to find the middle man who posed as Agnes's husband to make the safe deposit drops for Tanya. The clock is ticking.
The team realizes that the priest who performed the bogus funeral ceremony for Tanya is their middle man. The good father says the family is hiding in Ithaca. The local police storm the house and are able to take Brandt down. Needless to the say, the NYC team is overjoyed at the news. Esposito and Ryan are so jazzed that they're headed out on a four-hour drive to Ithaca.
Castle has other plans. Martha went to town to prepare a celebratory dinner for the family which, of course, includes Beckett. But gatherings like this won't be including Ashley in the future. Alexis lets him know that they are over. As for Castle, he's just beginning to rattle off all the times he's saved Beckett's life. It seems he's been keeping score. Even after this recent bank robbery adventure, Castle still holds the lead 9-8. How many life-saving moments can you remember?