Malone rides toward Paradine’s headquarters, following the signs, and finally locates the oasis casino. Paradine greets him at the door and compliments him as the brilliant head of the Secret Service. Malone isn’t happy that anyone knows who he is, but Paradine assures him that his secret is safe with him. he admits that Paradine isn’t what he was expecting, but Paradine claims that he’s impressed and invites him in to freshen up.
Inside, the two men share champagne and Malone explains that he’s looking for Jim and Artie. Paradine tells him that they’re on a fishing trip because they were satisfied that Paradine didn’t kill his brothers. He claims that he loved them and wants to find the real killer, and suggests that Malone join them. When Malone refuses since he hates fishing, Paradine offers the services of his two saloon girls, Daphne and Yvonne. Malone accepts and invites them to sit with him as Paradine leaves.
Still tied up from the roof of the tiger cage, the two agents swing back and forth until they can grab a rope and pull themselves clear. They try to escape only to find Paradine and his two hulks waiting for them. He offers them a choice of one of two curtains or what’s in a basket, and only gives them a few seconds to choose. Jim chooses the basket and Paradine congratulates him, telling him that he’s chosen a slow death over a quick painless one.
The hulks take Jim to the Snake Pit Lounge while Artie slips away. Jim is tied up and placed in the middle of a pit and the audience watches as a woman opens a basket and an elderly snake charmer comes out. It’s a disguised Artie, who charms the cobra into coming out and then puts it into a trance. Artie then offers to transform the ropes tying Jim into cobras, and asks for the hulks to volunteer. The hulks untie Jim and Artie ties them up as part of his act, and then he and Jim run for it. They steal two saddled zebras and ride off, and Artie explains that he and the real snake charmer are old stage buddies.
Juanita and her brothers open fire on them, forcing the agents to take cover. Jim admits that he left Mexico so he wouldn’t have to deal with them, and tells Artie to pin them down while he circles around and drops onto Juanita. He asks her what it’s all about and she explains that because of Jim, she turned down the governor’s proposal of marriage. Juanita apologizes and Jim tells her to get her family to stop shooting at them. She does so and then she and Jim kiss.
Back in Parsons Ridge, Jim and Artie confirm that they have authority through to Washington and there’s no way that Paradine can beat them there. The agents find Malone waiting for them and he explains that Secretary of State Messenger ordered him there. They tell him that Paradine is heading for Washington to disrupt the peace conference, a conference Malone didn’t know about. Malone says that he ran into Edney, who was leaving town to file another complaint against the agents. They spot a hot-air balloon passing overhead and board the train, unaware that the balloon belongs to Paradine.
heads east and Jim, Artie, and Malone spot the hot-air balloon again, but fail to recognize it. When they arrive in Washington, the agents meet with Messenger. He wonders why they didn’t develop invisibility first and notes that there have been some strange occurrences that could involve an invisibility man. Messenger warns them that the peace conference is to be his moment of triumph and he doesn’t plan to have them disrupt it. Artie says that he’ll infiltrate the peace conference in disguise, while Messenger explains that he sent Malone to Nevada because he’s bungler. He then tells the agents to go away, and the agents have to admit that Messenger might be able to pull off the disarmament conference.
Artie disguises himself as the Lichtenstein ambassador while Jim forges his papers. They plan to keep in touch through Messenger and Artie then goes to the meeting with the other ambassadors. He walks past Paradine, wearing the exactly same disguise, and the villain greets Artie before slipping away. Artie returns to the hotel where the agents are staying and tells Jim what happened. Jim has two tickets to the spectators’ gallery at the peace conference, figuring Paradine will be there. Artie realizes that Paradine was invisibly in the hotel room when Artie put on his disguise and they quickly leave.
Later, Messenger calls the conference to order while agents try without success to spot Paradine. Before Messenger can speak, the Russian ambassador interrupts to ask the German ambassador why his government has moved troops into Cuba. The German government denies the charges but the Spanish ambassador admits that they’re for training purposes. The ambassadors bicker back and forth until they resolve the matter. However, a fight breaks out and the ambassadors are soon at each other’s throats. The agents realize that Paradine had nothing to do with it and leave.
Back at the hotel, the agents find Paradine waiting for them. He complains that the war isn’t breaking out as he planned, and that everyone has aligned against Spain and Italy. They convince Paradine to boast of his plan to plant his bombs in the major capitals of the world and detonate one. However, he tells them that as a test of their skills, they will have to find the bombs. Jim agrees and then locks the doors, but Paradine turns invisible and evades them, escaping through the window.
With ten hours to track down Paradine before he triggers the bomb, the agents take to the streets. They spot Yvonne and Daphne going into a hotel and join them for champagne. The sisters admit that they know where the bomb is and Jim reminds them that the fate of the world hangs in the balance. They still refuse to talk and Jim grabs Daphne and drags her into the bedroom, saying he’ll do what he has to. Once they’re alone, Jim kisses her. She refuses to talk but kisses him back.
A few hours later, Jim comes out and finds Yvonne sleeping in Artie’s arms. He tells his partner that Daphne told him that the bomb is in Washington and set to go off at 9 a.m. Messenger has called an emergency session to get the delegates to make up, and Paradine has planted a bomb in the State Department building.
Messenger meets with the agents and refuses to erase everything that he has accomplished. He sends them to find the bomb and Jim returns to the hotel to kiss Daphne when she wakes up. She wonders if she’ll see him again if she tells, and Jim swears. Daphne then tells him the bomb is hidden directly below the conference room floor. As Jim leaves, he realizes that he just kissed Yvonne.
An invisible Paradine arrives at the State Department by carriage. Inside, the hulks capture the two agents, who realize that Yvonne and Daphne set them up.
The ambassadors enter the conference room and Messenger greets each one. They set down their cases and the invisible Paradine replaces one of them with his own.
In the basement, the steam pressure starts to rise to dangerous levels. Jim releases the steam valve, blinding the hulks long enough to cut himself free and then free Artie. As the agents go upstairs, Daphne and Yvonne arrive and explain that Paradine forced them to betray them. The women tell the agents where the bomb is and they race off.
Messenger gives his opening speech just as the agents run in and announce that there’s a bomb. Everyone panics and Messenger orders the ambassadors to stay. Artie has them check their briefcases and they find nothing, but the agents realize they haven’t checked Messenger’s case. They find the bomb inside as Paradine appears and congratulates them. He explains that when he’s invisible he’s also invulnerable, and is there to watch the bomb go off. However, when Paradine tries to disappear, he discovers that his device has malfunctioned. Paradine panics, saying there isn’t enough time to defuse his bomb, and Messenger orders Artie to do it. Artie opens it and pulls the wires, shutting it down just in time.
Edney promptly emerges and handcuffs Paradine to himself. Messenger wants the invisibility device and Jim warns the British agent that he’s out of his jurisdiction. Edney turns Paradine over to them and leaves back to Great Britain for good. Messenger tells the ambassadors to get out and then tells Paradine to come with him to discuss their secrets. Paradine regrets the lack of destruction, but Messenger tells him that there’ll be another chance. As Artie examines the invisibility device, Jim admits that they may be getting too old.
Outside, Messenger and Paradine are handcuffed together and suddenly discover that they’re invisible. Meanwhile, Artie tells Jim that he got the invisibility device working again and Jim tosses it into the Potomac. They pick up Daphne and Yvonne, who say that they’ve decided to stay another week. Messenger and Paradine find them and ask for the activator, and Jim explains that it’s in the water. As they go to find it, the two invisible men argue among themselves. And the agents take Paradine’s hot-air balloon and fly off with the ladies.
In Washington in 1980, Malone’s descendent gives a statement to the audience, showing them the invisibility actuator but discussing it as absurd. He then turns it on and disappears.