James West goes to the Serbian Embassy meets with the Minister. They go to the minister's office and discuss the International Jewel Exhibition in seven days. Serbia is going to display a 200-karat diamond, and Jim is there to request that the Serbians allow the U.S. Government to put the diamond into protective custody. Jim warns that there have been several mysterious and daring diamond thefts in the last few weeks. The Minister notes that they have adequate security, and Jim identifies all of the security precautions, including the hidden ones. The Minister, impressed, admits that the diamond is in the office and reveals where it is hidden. West is still unimpressed, and the Minister takes him to the window to show the exterior precautions. Suddenly the door to the office slams open and close, and the case explodes. When the two men go to the shattered case, they discover that the diamond has disappeared and someone has left a newspaper headline about the theft.
The Minister assumes that Jim staged the disappearance as proof of the flawed security, and demands the diamond back. He doesn't believe Jim's denials and orders his men to take the Secret Service agent into custody. Jim fights back and uses a cane with a smoke projector to cover his escape as he leaps out the window
At the home of Lady Margaret Midas, Morgan Midas and his manservant remove a trunk from the house, load it onto a carriage, and drive away. Artie arrives to see Lady Margaret and knocks on the door. The butler, Rudd, proves less than responsive, and a woman comes to the door. She says that her aunt left suddenly. Artie is surprised since Margaret just contacted him about arranging for the protection of her diamonds, the Queen Anne Triplet, which she was going to display at the Exhibition. When Artie demands to know who the woman is, she slams the door in her face.
Back at the train, Jim and Artie play billiards and discuss the case. In each instance, the thief only takes diamonds and ignores other gems, and nobody ever sees him or her even in broad daylight. Artie speculates that someone may have caused the diamonds to explode from within. Special Envoy Thaddeus Baines from Washington arrives. He's unhappy that Jim started an international incident with the Serbians. Baines is there to make sure that the Exhibition reflects credit on the government. Jim insists there was nothing he could have done, but has no theories to offer. Artie suggests his explosion theory, and Baines notes that it's as unlikely as a billiard ball exploding. Jim grabs the ball and throws it out the window just before it explodes.
Jim goes to Lady Margaret's home and asks to see Lady Margaret. The manservant, Clive, lets him inside and Jim waits in the parlor, where he sees Margaret's cat. The woman comes in with Midas and they explain that Morgan's aunt, Margaret, has gone on a long voyage. Midas introduces the woman, Lucretia Ivronin, as his fiancée, and claims that Lady Margaret was suffering from gout. Lucretia apologizes for her abrupt treatment of Artie earlier, and Jim asks for the diamonds. Midas refuses to let them leave the house without his aunt's specific consent, but Jim has a letter confirming Margaret's wishes. Lucretia notes that the diamonds are in the safe and they don't have the combination, but Jim offers to crack the safe's lock. Midas gives in and has Lucretia show Jim the safe while he steps out. Jim gets it open but is less than surprised to discover that it's empty. He insists that they have to come with him, and Lucretia kisses him. Suddenly some unseen forces whistles through the air and knocks Jim unconscious. Midas appears out of nowhere, smiling triumphantly.
At the Exhibition Hall, Baines comes to see the new security devices that Artie has installed. Artie invites him to touch the display case, which sets off an automatic camera. When Baines asks if they have more positive protection, Artie indicates the display case that will hold the most expensive case. Baines sets it off and the top of the case drops down. Pressure plates at the entrance will cause barred grates to close. Baines warns Artie that the government is assuming full responsibility for the thefts, Baines wonders where Jim is, and Artie assures him that Jim is working on the case, and he's perfectly all right.
Midas has taken Jim to his laboratory, hung him from metal bars, and super-charged him. He suggests that Jim knows something about his current project, but Jim explains that he's there to protect the diamonds at the Exhibition. Midas informs him that he's too late and explains that he's melted the diamonds at 4,000 degrees. He demands to know what Jim knows and tortures him with electricity. Jim insists he knows nothing, and asks if Midas killed Margaret. He points out that Margaret never goes anywhere without her cat, and then claims he's forgotten. Midas admits that electricity can interfere with memory, and starts to feed more electricity. Lucretia comes in and objects to Midas killing Jim. Midas steps out to run an errand, and Lucretia tells Jim that she just saved his life.
Artie, disguised as Count Baron Felix von Schlesweig und Holtbergen, arrives at house and demands to see Lady Margaret. Midas tells him that she's not home, but Artie insists that Margaret knew he was coming. He says that he's an old friend and will wait until she returns. Midas says he'll send his fiancée down to entertain him and then goes back to his lab. Once he's alone, Artie starts searching the parlor.
Midas tells Lucretia to get rid of Artie while he monitors the burning process. Jim feigns unconsciousness and then gets a knife from his boot and starts to cut himself free.
Lucretia thinks that Artie looks familiar. He says that he has to talk to Margaret about a friend who is in trouble.
Midas sees Jim freeing himself and runs over, but Jim knocks him over. Artie hears the commotion up above as the two men struggles, drops his impersonation, and runs upstairs. The two manservants attack him. Meanwhile, Midas runs out of the laboratory and his men attack Jim as well. Midas takes advantage of the diversion to run back to his laboratory, while Jim and Artie dispose of their opponents. As they head upstairs, there's a sudden whistling noise and Artie is knocked unconscious with extreme force. Midas appears on the stairs in front of Jim, but disappears before Jim can hit him. The same force smashes Jim unconscious.
Jim and Artie wake up in the laboratory, tied back to back. Lucretia comes in and serves them water, When Artie asks what hit them, she warns him that he won't believe her. Lucretia then says that Midas hit them, and that no one could see him because he was moving too fast. Midas uses the fluid distilled from the diamonds to accelerate his metabolism. They accept the explanation, and Lucretia tells them that she wants money and Midas is invulnerable once he drinks the fluid. She admits she likes Jim and advises him not to try and fight. He suggests that she help then, but she says she'd rather have the money and kisses him goodbye.
At the exhibit, Midas and Lucretia arrive and check the diamonds, and he assures her they'll be enough to give him the power to do whatever he pleases. He assures Lucretia that nothing can go wrong and that he has plenty of fluid. Midas then returns to the house and offers them a proposition. He offers them wealth and power as partners in return for them telling him what they know about the security arrangements at the Exhibition. If they refuse, he'll either kill them or destroy their minds. They accept, but Midas figures they plan to trip him up. However, he offers them a sip of the diamond elixir so they can see what power it confers.
Midas handcuffs Artie and Jim together and takes them to the Exhibition by carriage. He then pours them a bit of the elixir and takes twice as much for himself. They feel a brief burning and dizziness, and then recover. They don't notice anything different at first, but Midas ushers them out of the carriage and they realize everyone on the street is seemingly frozen. Midas puts the gun away and explains that it's useless. He then drops the flask... but it hangs in the air, falling too slowly for them to perceive in their accelerated state.
As they go in, Midas warns them not to stand still too long or they can be seen. As they enter the exhibit hall, they hear a clicking noise and Midas explains it's the separate vibrations of the sound waves of people talking. He admits that air friction can pose a danger if they move too fast. Midas then draws a knife to threaten Jim and demands that Artie tell him about the security measures. Artie explains all of the measures and Midas is confident he can resist them. He starts collecting diamonds and goes to the main case. Artie tells Jim to step on the pressure plate as they go out. As they start to leave, Artie and Jim wince in pain and Midas tells them the elixir is wearing off for them. As they slow down, Midas plants one of the stolen diamond bracelets on them and accelerates out of sight as they revert to normal time. The traps go off and the agents find themselves caught between the gates.
In jail, Jim wonders how they can stop Midas before he distills enough elixir to become unstoppable. Jim borrows a cigar from Artie and has a guard light it. He tells the guard to tell Baines they're ready to talk, and the man leaves. Jim then uses the torch inside of the cigar to burn through the bars. The agents then go to the house and confirm all the windows and doors are locked except an upper-story window. The agents rig a makeshift seesaw and Artie leaps on one side, propelling Jim up to the window. He goes inside and opens the back door for Artie. Jim tells Artie to create a distraction and attract the guards, while he deals with Midas.
After sampling the stroganoff, Artie starts banging pots and Clive and Rudd come running in. He quickly disposes of them. Upstairs Midas, goes to investigate and Jim runs in, He knocks Midas down, and Midas tells Lucretia to shoot. When she hesitates, Midas drinks most of the elixir. Jim grabs the flask and drinks the rest, but Midas warns that he took much more. Lucretia throws Jim the gun but it comes to a stop in mid-air. The two men fight and Midas warns that they're moving too fast and will burn up from the air friction. Jim's dose starts to wear off and he knocks Midas back. He breaks a flask of alcohol and spills it on himself. and the heat ignites it. As Jim slows down to normal time, he and Lucretia watch as a brief burst of flame consumes Midas.
Jim goes down to the kitchen and discovers that Artie has the two manservants tied up. Artie admits that he cheated and used force.