The Middleman and Wendy are at Middleman HQ puzzling over two pictograms left on mirrors at the site of the thefts of a Beryllium sphere and an Oscillation Overthruster. The Middleman figures the villain is trying to reveal something about himself and spins a theory about the villain being the great-grandson of Tesla. Wendy and Ida aren't convinced. Even The Middleman decides they need to take a break and Wendy takes off for her date with Tyler. He shows up three hours late due to his new job with Manservant Neville, and gives Wendy a diamond tennis bracelet. The two of them exchange vows of love but they're interrupted when their respective bosses page them. The Middleman has another theory which Wendy quickly dismisses. Tyler admits that Neville has an emergency with uMaster and is sending someone to pick him up. Wendy thinks they have a few minutes but they're interrupted when Neville shows up in a helicopter.
The next morning, Lacey seeks to console Wendy who is crying over the events of the previous night. She wonders if the job with Fatboy could change Tyler. Lacey assures her that she thought the same thing when Wendy took on her new job, but nothing bad happened. Although Lacey had to lower her expectations a bit. Wendy is called off to work by The Middleman to investigate the theft of dolls' eyes from a toy factory. En route Wendy receives an apologetic call from Tyler and she says it's okay. Tyler tries to set up a date but Wendy has to pass because of her duties.
At the toy factory, the owner reveals that the hundred thousand doll eyes were made of polydichloride and the thief left a mirror with a drawing of a river on it. They realize that the three pictographs spell out a palindrome, and the polydichloride can be combined with the overthruster and the beryllium to activate a Quantum Singularity Machine. The Palindrome can open a portal to parallel dimensions. Ida comes up with an address for a power station with the proper energy readings. They go there and spot The Palindrome, wearing a black suit and a goatee. The air is filled with polydichloride gas which will ignite if they use their guns. Wendy sneaks around while The Middleman tries to taunt The Palindrome into monologuing. The Palindrome refuses to explain himself and activates his device. He's sucked into the gateway and The Middleman is knocked out by flying debris. Wendy tries to shut down the device and is sucked through the gateway before it closes.
Wendy wakes up as The Palindrome fleas with his device. She goes after him only to find that the entire city is different: it's a grimmer darker place where Manservant Neville speaks to the people as their father, broadcast over massive TV screens. The many homeless line up for soup sprays and when Wendy approaches, the security guard demand to see her ID. She flees and the guards pursue until they're called upon to give the Pledge. She calls The Middleman but gets no answer.
Going to her sublet, a hostile goatee-wearing Noser with a shotgun hails her and demands the correct lyrics to let her in. It turns out the sublet is now an exotic dance lounge and Joe 90 is an attorney to Fatboy with a high security clearance. He doesn't recognize Wendy but a brunette Lacey does. She punches Wendy and accuses her of betraying during their earlier years when their art school was bought out by Fatboy, and later when Wendy joined Fatboy and had Lacey arrested during a protest. Fatboy security guards show up and Wendy and Joe flee outside while Noser opens fire. Joe takes off rather than endanger his security clearance. A van pulls up and someone calls to Wendy to get in: Pip. Pip in the mirror universe is a priest and Wendy is astonished to find that he'll risk his life for her. Wendy realizes there can only be one person so good that he'd be the same in this new, evil universe. She asks Pip to take him there.
In the regular universe at Middleman HQ, The Middleman goes over a recording of what happened. The tape shows that a different Palindrome emerged from the Gateway, in a gray suit and no goatee. Ida realizes it's The Palindrome from the parallel universe and The Middleman is determined to recover the quantum singularity device.
Wendy goes to the temp agency to be greeted by a young attractive blonde with the same fashion sense as Ida. Wendy realizes it's the Ida of the mirror universe and tries to explain, but Ida isn't interested and just wants money. She takes Wendy to see the mirror Middleman, who has an eye patch, long hair, and chaps. He's working on his Middlehog and already knows about the rip in space time and recognizes her gun. Wendy insists it's his business now but he's not interested unless she pays. She doesn't have any Fatboy currency but offers to pay him with Tyler's diamond bracelet. He has Ida fire up the HEYDAR. In both universes, Ida IDs the man on the tape as an Ivan Avi and gets a home address. Both Middlemen (and Wendy in the mirror universe) confront each Ivan, but each one destroys his quantum singularity machine.
While the mirror Middleman prepares to torture the mirror Palindrome, the regular Middleman gets the regular Palindrome to explain once he says that Wendy was exchanged. The Palindrome explains he was born an orphan in an evil world, and left his clues as an artistic statement. When he was 13 he severed his pineal gland and started getting visions from his mirror-stuff, trapped in the regular world and lost his pineal gland. They communicated and pooled their talents to build a quantum singularity machine to get to their "correct" universes. Although the machine can't be built, The Palindrome notes that a phased polaron cannon can be used in both universes to create a singularity. If an individual in each universe fires it at the same time at the same black hole, it'll create a rift. Fortunately, The Middleman has a phased polaron cannon in the weapons archive.
The regular Palindrome mentally contacts his mirror version, who the mirror Middleman is beating up. Wendy stops him with a martial arts move that the mirror Middleman recognizes as belonging to the psychotic Sensei Ping (who took out the mirror Middleman's eye). The mirror Palindrome relates the plan and the coordinates to fire the phased polaron cannon at. When Wendy asks him to send a message, the mirror Palindrome grabs her gun but the mirror Middleman shoots and kills him. Wendy is less than thrilled and is even more unhappy when she finds out The Middleman sold his version of the phased polaron cannon to Fatboy Industries to pay the rent. As the mirror Middleman stalks off, mirror Ida explains that he used to be a force for good until his Middleboy, Tyler, was killed by an unseen killer with a red anodized ray gun. Mirror Ida figures the phased polaron cannon is at Manservant Neville's control center.
Wendy goes to Lacey's to ask for her help getting into Fatboy Command, offering her a chance for revenge. When that doesn't work: Wendy gives her an apology for all the things her mirror counterpart did to her. Lacey agrees to help and supplies blackmail evidence against Joe 90. They force him to let them in. Meanwhile, mirror Ida confronts mirror Middleman and tries to get him to help, but he doesn't care. When he refuses, she quits.
Wendy breaks into Neville's armory, noting the security combination seems familiar. They find the phased polaron cannon… and the cryogenically frozen Manservant Neville. Neville revives enough to recognize Wendy and beg to be put out of his misery. He admits he tried to return control to the people, but Wendy betrayed him. The mirror Wendy arrives, holding a red anodized ray gun. She has her own HEYDAR and detected Wendy's arrival. Mirror Wendy admits she killed Tyler and used the date of her father's disappearance as the combination for the control room. She wanted to be in control and infiltrated Fatboy as Neville's assistant, then betrayed him and secretly took control of Fatboy Industries. Joe 90 admits that he set off a silent alarm and betrayed them. Mirror Wendy kills him and prepares to dispose of Wendy and mirror Lacey. Wendy uses her training from Sensei Ping to knock out her counterpart. Wendy dons her counterpart's clothing and prepares to leave holding Lacey as a prisoner. However, mirror Wendy has an ID card proving her identity.
Things look grim but the mirror Middleman arrives on his Middlehog and subdues the guards. They grab the phased polaron cannon and escape to the designated coordinates. The mirror Middleman plans to leave the city once he sends Wendy back. She thanks him and he insists she shouldn't make him her hero. Mirror Lacey is glad that the Wendy she knew is still alive somewhere. The two Middlemen fire the phased polaron cannons in sequence, but as Wendy leaves she tells the mirror Middleman to fight. She goes through the gateway and the two Middleman exchange salutes before the rift closes. The mirror Middleman admits he was impressed with mirror Lacey and offers her a job in the field of temporary employment.
The Middleman drops Wendy off at her sublet and wonders what his other self was like. Wendy assures him that the mirror Middleman had to be similar to her boss, and figures all of the Middlemen in all the parallel universes are like him. They wonder what will happen to that universe and if the mirror Middleman will step up. However, as Wendy goes into her apartment she finds Tyler's bracelet: the mirror Middleman slipped it back onto her when she wasn't looking.
Mirror Lacey comes into Middleman HQ in a new schoolgirl outfit. The mirror Middleman is shaving and Ida comes in to tell them not to get any ideas. The mirror Middleman reverts her to her "original" form and Ida declares it's time to kick some butt.
While Tyler sleeps in her bed, Wendy calls her mother to assure her that everything is going fine with Tyler, with her job, and with her boss. Her mother notes that she sounds happy and Wendy admits that all seems right with the world for her… as she looks at her painting of The Middleman.