"Crossfire" is the twenty-second episode of the eighth season the comedy-drama TV series Castle. It is the final episode of the series, and originally aired on ABC on May 16, 2016.
The episode starts out with someone driving a car, singing along to the song It's a Sunshine Day, only to stop near an abandoned factory and torch his car containing a restrained man in the boot. Then we are shown Castle and Beckett, heading to the location Caleb told them the mobile he gave them would be able to receive a call from Locksat. Unfortunately, they are not able to trace the call and the voice over the phone being electronically modified, they are left with no way of identifying nor locating the caller.
Beckett, Castle, Hayley and Vikram decide to spy on Caleb while he comes to the rendezvous point chosen by Locksat, in order to identify the mystery man. Meanwhile, Ryan and Esposito arrive at a crime scene, where a burnt corpse has been found in the boot of a car. They call Beckett and reveal to her at the worst possible moment that the corpse in the trunk is none other than Caleb Brown. Castle and Beckett are taken aback, and soon realise that it was a trap. Thanks to Hayley's skills with a sniper rifle, they manage to stay alive long enough to see an impromptu Korean tacos truck get in the way of their assailants. It turns out that the driver - Mason Wood, the leader of the Greatest Detectives Society - was sent by Castle's stepmother. Mason leaves them in a safe place, insisting that he does not want to know anything about the man or organization that they are fighting against, fearing for his safety.
Castle returns to his detective agency to meet with his family and Hayley while Beckett goes to the 12th precinct, where she finds out that Vikram has told Ryan and Espo all about Locksat. She ends up begrudgingly explaining everything she knows, she asks them to stay out of it but they refuse and go after a new track, going so far as forcing her to stay put. At the same time, Castle, restless as always, decides to go to the precinct as well, but ends up being detained by the man who burnt the car at the beginning of the episode.
Shortly after, Beckett receives a call from Mason, who tells her that he may have a lead and that he will meet his informant this very evening, but Beckett insists on coming with him until he reluctantly agrees.
Then we see Castle, tied up, being injected with truth-serum and forced to reveal the names of all people around him who knows about Locksat to the man himself, who turns out to be Mason. Castle can't contain his tears when he reveals that his mother and his daughter know about Locksat, because he knows that the man will kill all those who know about him. He tells Richard that he now has to meet with Beckett and leaves him to be killed with a lethal poison administered by his right-hand man.
Vikram discovers the phone number of the killer and then successfully locates the CIA building where the killer is hiding. Ryan and Esposito come to rescue Castle with a whole NYPD squad, fight their way through the building and get to him just in time. Mr. Flynn, Locksat's right-hand man, is injected with the truth-serum by Castle, and ends up confessing that Mason is bringing Beckett to that same building, in the basement room where Castle's body was supposed to be burnt down in a furnace. After what, we see Locksat picking Beckett up and taking her to the building where Castle is.
Castle, trapped in the room because of the ongoing gun battle between the NYPD and the CIA, has to get out through the wall and climb his way down alone, Ryan and Esposito covering him. Meanwhile, Mason has led Beckett to the basement and to his surprise, she pulls a gun on him and tells him to drop the act. But Mason had an ace up his sleeve all along, and despite Beckett pointing a gun at him, he disarms her thanks to a remote-controlled powerful magnet mounted on the ceiling, while his plastic-made gun remains in his possession. Before pulling the trigger, he tells her that Castle is dead and that his body is being burnt in the furnace right in front of her, saying that it is a fitting end for their love story to end up in the same fire. But Castle shows up behind him, gun in hand, and calls him out. Although his gun ends up on the ceiling, it gives Beckett an opportunity to disarm and arrest Locksat.
After that, Castle and Beckett meet with their family and friends (Lanie, Espo, Ryan, Vikram, Martha, Alexis and Hayley), some of them decide to go celebrate in a bar, but Castle and Beckett head home to rest. Suddenly, Castle starts wondering aloud why Locksat got rid of the body of Caleb by leaving it to be potentially discovered in the boot of a car, where the police would find it, while they had a furnace in the building. At the same time, out of the blue, Caleb shows up and shoots Richard. Beckett comes running and fires back at Caleb, who drops dead on the floor. But we see that he has also shot Beckett several times and she falls down on the floor as well. Then Castle and Beckett crawl on the floor towards each other, until their hands meet.
After this dramatic scene we see how, seven years later, Castle and Beckett are still happy together, playing with their three children. The episode ends with Castle saying "Every writer needs inspiration. And I found mine.", to what Beckett answers "Always.", Castle nods and agrees with the same word: "Always ."
The episode was written by executives producers Alexi Hawley & Terence Paul Winter , It was directed by Rob Bowman.
The original broadcast had 7.65 million viewers the episode received mostly positive reviews but fans were divided about the finale as they argue that it was very rushed in storytelling.