Jim and Barney are in the Caribbean for a two-week vacation, and Barney is dating a local painter, Alma Ross. They are at Alma’s apartment in Cuidamo, dancing, unaware that a drunken man is outside with a knife. Meanwhile, Barney assures Alma that he’ll see her the next time that she’s showing her paintings in the States. She worries about losing him and they kiss, and then Barney leaves for the night. He doesn’t see the armed man, Luis Corba, who goes into Alma’s apartment. Meanwhile, Barney decides to buy some flowers and have them delivered to Alma.
In the apartment, Alma assumes that it’s Barney knocking on her door and opens it. Luis advances on her, jealously demanding to know who Barney is. He advances on Alma and demands to know why he’s no longer welcome. She screams and Barney hears her and runs back. They struggle and Luis finally lunges at Barney, misses, and falls out the window, landing on the knife. Barney confirms that he’s dead and has Alma call the police and Jim at the hotel. Alma warns him that Luis is the brother of the Manuel Corba, the chief of police.
At his office, Corba is meeting with Riva, a petty hustler who has been arrested several times for gambling. Corba is dealing with Riva arrested when Lt. Jocaro arrives, The police chief has his sergeant take Riva away and Jocaro tells his superior that Luis is dead.
Jim is at the hotel when Alma calls him. She warns him that Corba has a reputation for ruthlessness and Jim promises to hire the best lawyer in town.
Riva is taken to Room #10 by several officers and realizes that they are Corba’s death squad. Screaming and squirming, Riva is hauled into the cell.
As Luis’ body is taken away, Corba disputes Barney’s story, claiming that Luis didn’t have a knife and wouldn’t force his attention on a woman. He accuses Barney of lying but the flower man steps forward and confirms that Barney was in the street when Alma screamed. Jocaro takes him away to get his statement while Corba establishes why Barney is in the country and how he met Alma. Even after Barney confirms that he was referred to Alma by an art director in New York, Corba puts him under arrest for murder.
Jim and Alma hire a local lawyer, Tolima, but Corba is unimpressed and tells them that Barney has no rights in their country. He plans to hold Barney incommunicado and talks to the lawyer privately. Once they’re alone, Corba starts talking to Tolima about his future.
Jocaro and the death squad take Barney to Room #10, which contains several high-security cells. As Riva begs Jocaro to let him go, Barney asks about his lawyer and the lieutenant claims he knows nothing about it. Once Barney is locked up, Jocaro has Riva’s cell opened and advances on him.
Tolima comes back and tells Jim and Alma that he is withdrawing from the case, insisting that Barney is guilty of premeditated murder and Alma is lying. Jim realizes what Corba has done. Later, he approaches Tolima and demands an explanation.
Paris is returning home when he gets a call from Jim explaining what’s going on. Jim says that he’ll get started where he’s at while Paris and Willy fly down and bring some things.
Barney tosses a wet cloth to the beaten Riva and introduces himself. Riva wonders why he’s there and explains that Cell Block 10 is where the death squad keeps the condemned awaiting execution.
Jim tells Willy and Paris that Corba threatened to kill Tolima if he didn’t withdraw from the case, and has made the flower man disappear. Before Corba became the police chief, he was the executioner at the prison and enjoyed what he did. There have been over 70 executions, and the governor dismisses the accusations as rumors because all of the bodies have disappeared. Willy has fake Interpol identification, and Paris has two fake IDs as a police officer and a jewelry fence. The key is one of Corba’s victims, a petty thief named Felice Guamore.
Riva tells Barney that he won’t make it to court the next day, and Barney decides he needs to break out. He looks at a caged light bulb and the wire frame of his mattress, and asks Riva for a pencil.
Jim warns that the cell block is too well guarded and that they can’t count on Corba keeping Barney there. They plan to go after Jocaro, who is on the take, and figure that Corba needs the money to fund his political aspirations. Alma calls to ask Jim to come over and meet with her. He agrees and tells the others that they can’t reveal their true identities to Alma. According to Tolima, Barney will be killed at a specific place of execution rather than in his cell, and they have to keep their teammate alive until they find it.
Barney strips the wires from the wire frame bunk.
Willy comes to see Corba posing as an Interpol inspector and tells the police chief that Jim and Barney are jewel thieves working together. They’re responsible for the theft of emeralds in the country a month ago. Corba lies and says that he has no information on them. As he goes, Willy says that Guamore was the getaway driver in the robbery and Corba says they’ll try to find him. Corba then tells Jocaro that they’ll delay Barney’s execution for a few hours.
Jim tries to reassure Alma, who admits that she loves Barney and asks him not to let Barney die.
Barney removes the light bulb from the socket and runs the wire from the mattress over to his cells’ electronic door lock. Riva looks on, impressed.
Paris, posing as a police officer on transfer, comes to see Jocaro. As he presents his papers, Paris “accidentally” flashes a wad of bills, piquing Jocaro’s interest. After examining the papers, Jocaro points that Paris isn’t due to report until tomorrow, and Paris says that he’ll kill time by taking in the sights of Cuidamo. He asks for directions to the most expensive hotel, restaurant, and girls, and thanks Jocaro for his help. As he leaves, Paris invites him to a party at his hotel room.
Riva admires Barney’s work and admits that he was never a very good bookie. As Barney starts to cut through the lock panel with his makeshift arc-welder, he assures Riva that he won’t leave him.
Corba comes to see Jim and tells him that Barney is doing well. He then tells Jim about his visit from Interpol and that he knows Jim is a jewel thief.
Barney gets his cell door open and goes to the panel controlling Riva’s door, but Jocaro comes in for an inspection and recaptures them.
Corba threatens to turn Jim over to Interpol unless he gives him a share in the stolen emeralds. Jim admits that he doesn’t know where they are but Barney does. Corba figures that Barney will talk to Jim and lets Jim meet with the prisoner. The two agents talk while Corba watches via a two-way mirror, and Jim uses a matchbook to let Barney know that they’re under surveillance. As they stage a fake conversation, Jim tells Barney to say that he’ll think it over, and then asks him to say where the emeralds are hidden. Barney says that he’ll think it over and Corba signals to have the interview ended. Afterward, Jim assures him that it will only be a matter of time, but the police chief isn’t so sure.
Paris brings in two local girls to party with him and Jocaro. As Paris gets increasingly (fake) drunk, he tells Jocaro that he wants to be part of the death squad and asks him to put in a good word with Corba. Paris then passes out and Jocaro orders the two women out. He pays them out of the money from Paris’ wallet, sends them away, and then checks the wallet. He finds a second ID for Paris under a different name, as well as newspaper clippings about Guamore’s disappearance and the emerald theft. Jocaro then tosses water into Paris’ face to wake him up and demands to know why he’s really there. Paris admits that he deals in jewelry and explains that they can both be rich. He asks where Guamore is, explaining that he was supposed to fence the emeralds and knows that Guamore took the largest emerald for himself and had it on him. When Jocaro says that the prisoners were searched, Paris explains that Guamore had a pocket watch with a secret compartment. The lieutenant says that the death squad is a fantasy and he has no idea where Guamore is, and takes Paris’ money and orders him out of town. Jocaro then leaves and Jim and Willy follow him.
Jocaro goes to a warehouse and goes through the belongings from the executed prisoners. As he checks each watch for the emerald, Jim and Willy come in and find a gallows, a duplicate of the one at the federal prison where Corba served as executioner. Meanwhile, a disgusted Jocaro gives up and comes out, and the two agents hide. Once he leaves, they find the cabinet with the dead men’s belongings as well as a tank of sulfuric acid. They have enough evidence to convince the governor but no in time to save Barney. Jim has Willy bring Paris to the warehouse.
Alma comes to see Barney while Corba watches. He assures her that he’ll be all right, and Alma says that Corba has told him that he and Jim are jewel thieves and that Corba will release Barney if he tells where the emeralds are hidden. Barney insists that Corba will have him killed once he talks and she realizes that her lover won’t talk no matter what. Alma says that she’ll beg Corba for his life but Barney tells her to stay away from the police chief. Corba comes in to end the interview, has Barney taken away, and tells Alma that she can buy Barney’s freedom.
Jim and Willy rig the gallows, putting in breakaway ropes. Paris warns them when the death squad arrives with Barney and Riva, and then takes the prisoners’ belongings out to the car. In the basement, Jim barricades the door while Willy sets up an elevated platform beneath the gallows. Once the death squad is inside, Paris sabotages the police van and the radio.
Corba pronounces sentence on Barney and Riva and they are taken up the gallows. Jocaro offers them hoods but Barney refuses. After a moment, Riva, inspired by his new friend, also refuses. Corba gives the order and Jocaro pulls the lever... and Barney and Riva’s ropes break, they fall through onto the platform below, and Willy and Jim get them out. Corba takes his men to the basement and they try to break through the jammed door. By the time they get through, the IMF has already made its escape. When Corba and his men try to pursue, their van doesn’t work.
Alma is doing a sketch of Barney when he comes to see her. He tells her that he’s taking her back to the States and that they’ve sent the evidence on Corba to the governor, and escorts her out to the IMF car to make their escape.