In Kansas City, industrialist Curtis Langley Dodd is at home playing the piano, unaware that a crossbow is mounted inside. Dodd’s butler Griffin answers the door to find Jim and Artie there. They ask to see Dodd but the butler refuses to let them in. When they hear the piano playing, Jim grabs Griffin and demands that he confirm that Dodd is playing the piano. When he does, Jim insists that he open the door. Griffin does so but then calls in two manservants to deal with agents. Jim goes to find Dodd and runs into Elaine Dodd, Dodd’s wife. She insists that he leave but Jim says that her husband is danger. He goes to the lounge and tells Dodd to stop, just as Griffin comes in with a gun. As Jim struggles for the gun, the crossbow goes off, killing Dodd.
Later at the Wanderer
, the agents and their superior, Colonel Crockett, meet with Elaine. She worries that her actions may have led to her husband’s death, but Crockett assures her that she’s not to blame. Once Elaine leaves, Crockett tells the agents that there’s been no word from Washington except Grant offering his condolences for the death of Dodd, the most recent in the series of “alphabet killings.” They go over a list of the departed, each one a rich industrialist. Dodd is the fourth. The agents explain that they discovered that each victim died on a holiday, and the prior day was Easter. Crockett warns that President Grant is worried that if someone could take control of the holdings of enough industrialists, they could disrupt the country’s workings. As they consider who the next victim might be, Crockett’s secretary Gates comes in and reminds Crockett that he has a Senate committee meeting. Once he leaves, Jim finds a sympathy note that Elaine has left for them and realizes that the note has the same decorative M with a broken serif.
That night, Artie continues his analysis and confirms that both cards were printed in the same print shop. They get a wire informing them that the cardstock comes from only one place, the Friendly Card Company. The agents go there and find it closed for the night, and use a key under the mat to go in. As they go in, someone secretly watches them through a peephole. Jim and Artie go into the back and find an invitation from a Miss Emma Valentine, announcing the marriage of Michele Le Master to Paul J. Lambert, another wealthy industrialist.
As the agents talk, a cupid sculpture on the wall fire an arrow at them, narrowly missing. Two men burst through a hidden panel and attack them, while a third one emerges from the shadows and subdues Artie, and then puts him into a paper-cutting machine. The other two men try to hold Jim but he breaks free, knocks them out, and takes out the third man just in time to save Artie. Two of the men flee back through the hidden panel, sealing it behind them. The agents try to interrogate the remaining man, but someone outside shoots and kills him and flees.
The next day, Artie returns to the Wanderer
and tells Jim that the owner of the shop is one E.N. Itnelav. The dead man had no identification. Artie thinks that Elaine set them up but Jim isn’t so sure, and shows his partner Lambert’s wedding announcement. There’s also a newspaper article on Emma Valentine, Washington hostess who has arrived in Kansas City to manage the wedding. Artie notes that all of the dead men had married within the last six months to women much younger than themselves. He notes that Lambert doesn’t begin with an E, but they figure the killer deliberately used the pattern to distract them from the intended fifth victim.
While Artie goes to stop Lambert from marrying, Jim returns to the print shop and talks to Itnelav. Jim point out that there was a fight there the previous night but Itnelav says that it was closed and nothing could have happened there. As the agent asks to look around, Emma Valentine comes in to pick up a delivery and introduces herself. As Itnelav takes out the packages, Emma tells him that she wants him there as her new exciting guest at the reception that evening. Jim accepts and Emma departs at Itnelav returns, and Jim tells the printer that he’s found what he was looking for.
Artie talks to Lambert and tries to convince him to cancel the marriage. Lambert ignores him until Artie yells at him, and the cattle baron finally agrees to a delay. Michele comes in and Lambert can’t bring himself to delay the wedding and disappoint her.
As Jim breaks into Emma’s home, Emma exercises in her bedroom. Michele arrives to show her the wedding dress and is clearly upset. The hostess reminds her that she used to be a barmaid and now she’ll be married to the wealthiest man in America, and it took a lot of work to make her acceptable to win Lambert. A series of alarm bells go off and Emma confirms that the intruder is moving through the house and heading for the chapel. Emma goes to change so she can greet her guest.
Jim enters the chapel and Emma and her thugs come in. They subdue the agent and Emma tells him that he will soon have a harem with eager hands ready to crush the life out of him. When Jim wakes up, he finds himself held in place by artificial women’s arms. Emma demonstrates that she can trigger them at will to crush the agent, and then explains that she wants to avenge all the slights of men against women. He confirms that she has arranged the marriages and then deaths of the four industrialists. Emma controls the wives after they inherit their husbands’ wealth, and after Lambert’s death she will control enough wealth to make Congress obey her every demand and appoint her as Empress so she can assure equality for women.
Back at the Wanderer
, Artie meets with Crockett and try to figure out their next move. Artie looks at Itnelav’s card in a mirror and realizes that his name is “Valentine” spelled backward.
Emma continues to discuss how the country will flourish under her scientific reign, and that everyone will be happy because she will arrange happy marriages. She displays her Love Eternal machine, having cut a series of hearts into a piece of paper. When she feeds the paper into the machine, it calculates Jim’s perfect woman. Under Emma’s reign, she will only allow people to marry their proper mates. Upon running hr machine, Emma discovers that Jim’s perfect mate is a combination of perfect women. She flirts with him until Jim rejects her and she slaps him. Michele comes in with her wedding veils and Jim reminds her that she is working with a murderess. Lambert arrives and Emma goes to greet him.
Once they’re alone, Michele admits that she stole once and Jim says that it doesn’t make her a thief. Michele explains that Emma took her from a prison in France and could put her there, and that Emma controls all of her women through blackmail. He tells her to get out before she’s an accomplice to murder and asks her to release him. Before she can, one of Emma’s thugs returns.
Artie, disguised as a tailor, is measuring Lambert for his suit when Emma comes in to. As Artie tries to stall, admiring Emma’s dress and shamelessly flattering her, Elaine comes in. She whispers to Emma, who steps in as Artie rips the sleeve off of Lambert’s tuxedo. Once Lambert leaves, Elaine draws a gun on Artie and Emma rips off his fake beard, laughing in triumph as her thugs come in.
Emma has her men strap the agents to the stained glass chapel roof and explains that the organ hammers are fastened to the glass. Elaine will play the organ and play the proper chord, shattering the glass. She demonstrates, striking a chord and shattering a champagne glass. Once Elaine leaves, Emma says that the proper chord is sounded once at the end of the bridal recessional. The glass will shatter, killing Lambert and dropping the agents to their deaths. With Lambert dead, Emma will declares herself Queen Emma the Third. The organ begins and Emma leaves to attend the wedding.
In the chapel, Elaine plays the organ while Lambert wait at the altar and Michele is escorted in. The minister begins the ceremony while Emma glances up at the stained glass roof, unaware that Jim is cutting his leg rope on a loose nail. Once he frees his right leg. Jim uses his toe knife to cut his other leg free and then kick up and cut Artie’s hands free.
The minister pronounces Lambert and Michele man and wife. Elaine begins playing the recessional. Above, the agents fire grappling lines into the ceiling.
Emma has Lambert pose for a photo beneath the stained glass roof. Elaine plays the final chord and the stained glass shatters. The agents drop down and find Emma’s thugs, while Emma draws a gun. As she prepares to shoot Jim, Michele knocks her hand aside. The agents make short work of the thugs and Jim chases after Emma, who has slipped out in the confusion. Michele returns the wedding ring and says that she won’t give him any trouble having the wedding annulled.
Jim pursues Emma to her boudoir and finds the mating machine running. A piece of paper is on the counter with a message saying that Emma will show that crime pays. Jim runs to the window just in time to see Emma depart in a coach.
Later, the agents return to the Wanderer
and find a heart-shaped box of chocolates on the table. Jim notes that Emma had several hours to plan something before she was captured and sent to jail. Artie warns that it could be a bomb and Jim takes it to the window and throws it out. Nothing happens and Artie goes out to get it. He returns and shows his partner the now ruined chocolate-covered cherries. There’s a note saying that it came from Michele, inviting them to the wedding.