In Star City, lightning slams down and hits buildings. Diggle's team is in the field, and Curtis tells Diggle that it's following them. Diggle confronts Slade's son Kane and orders him to surrender. He charges forward and attacks them. As he takes them down, Oliver, Barry, and Supergirl arrive and take out Kane, and Diggle figures that there's some huge problem going on.
Later at ARGUS, the trio explain to Diggle and Curtis what has happened, and asks them to work out what is going on while they go to Gotham City. Oliver says that he already called Felicity, just as she arrives and Barry has to pretend that he's her husband because that's what she perceives him as. Barry is surprised to learn that things aren't good between Oliver and Felicity. Once Felicity and Curtis leave, Oliver and Barry tell Diggle that things didn't go well when they tried to explain to Barry's team, so they decided to keep Felicity out of the loop. As the trio leaves, Oliver suggests to Barry that he shouldn't go because "Oliver Queen" is a public figure and would draw attention in Gotham City. Oliver figures that Batman is an urban legend and doesn't really exist.
Supergirl flies Barry to star City and Oliver joins them. Oliver says that he knows a radio personality, Vesper Fairchild, and admits that he doesn't remember if he slept with her. They find a covered-over Batsignal on the roof.
On a tower atop Wayne Enterprises, a caped figure watches them.
The next day, the trio head for the radio station. An armored car pulls up and a rich man gets out with armed guards. A gang comes over and demands a "tax" from the out-of-towners. Oliver suggest that they talk it out, and the man draws a gun on him. When he shoots, Kara catches the bullet and Barry disarms the man. The GCPD pull up and order everyone down on the floor, and when they see Barry, they call in backup because they think he's Green Arrow. Oliver tells Barry to stand down, and after a moment he does so.
Felicity and Curtis run pattern recognition and Felicity points out that the energy appears to be a dimensional breach. Cisco and Caitlin arrive and say that they were getting the same disturbances in Central City until Barry and Oliver came to Star City. They mention "body swapping" and Felicity demands to know what's going on.
The trio sit in a cell and the officer on duty says that she called Laurel, who said that a night in jail would do them good. Barry tells Oliver that he handled the situation just like he was. Kara points out that they were both right and she would have just superspeeded them out. The officer comes over and says that someone posted their bail. The trio goes outside and finds a driver and SUV waiting for them. The driver shows a gun when they say that they'd rather not. They go to a building and the driver leaves them at the front door. It's an abandoned Wayne Enterprises building, and Olive says that Bruce Wayne disappeared three years ago and no one knows who he is. He explains that the Wayne Enterprise board worked with get-rich-quick operators once Bruce left. A woman, Kate Kane, is there and says that no one has seen Batman for years. She figures that once they find what they're looking for, they can get out of her city.
Cisco tells Felicity that Iris had problems with her husband not being who she thought. Felicity admits that her marriage with Oliver has become strained, and then figures that something is trying to come through the dimensions and they need to let the person through to stoop the lightning.
Oliver tells Kate that they already tried facial recognition, and Kate explains that when Batman left the city went to hell. Barry returns and says that Vesper hung up on him, and Kate tells them they can work out of the building. Oliver stole data from the GCPD.
Caitlin talks to Felicity privately and explains why Barry and Oliver though Oliver's team wouldn't believe them. Felicity isn't convinced and figures that it's another excuse for Oliver not trusting her. Caitlin says that as long as there is love, Felicity can't give up on it. Felicity thanks him and says that if they build a quantum flux anchor, whoever's trying to breach through will come.
Oliver finds the man in the drawing: John Deegan. Deegan was conducting experiments on his patients' brains, and he was fired and suspended five years ago. Kara prepares to do an x-ray flyover of the city to find Deegan. When she goes down, she finds Kate and apologies for questioning her earlier. Kate explains that Bruce is her cousin and she's in the process of turning the building into a real estate firm. Kara notes that her cousin is a friend with Bruce, and suggests that he might have "broke" from the strain of trying to keep his private life private. Kate insists that Bruce didn't leave Gotham without a fight. Kara asks her if she knows Deegan, and Kate says that he's a doctor at Arkham Asylum.
Once she's alone, Kate takes a private elevator to a subterranean lair beneath the building and goes to a Batman-like costume.
Felicity and the others go to the ARGUS roof to set up the device that will bring whatever is trying to breach through to them. Once it's ready, Felicity activates the device and a man who looks like Jay Garrick briefly appears and tells them that if they get the book then they can fix it.
The trio goes to Arkham and figure that they have to break in. Cisco, Caitlin, and Diggle breach there and tell them what the other Flash said about finding the book. Kara goes in pretending to be transferring Caitlin to treat her condition. Diggle and Oliver go in and look around, and find Deegan's laboratory. He knows who Oliver really is and boasts that changing reality itself has a bit of a learning curve. Oliver tells him to undo what he is, and Deegan wonders why he would want to and triggers an alarm. He throws a chemical vial, causing a smoke burst so that he can run out.
Throughout the asylum, the cell doors open. Kara dons her costume, while Oliver tells Diggle to get the prisoners into their rooms and find the book. Oliver speeds out, puts Barry's Green Arrow costume in, and Barry swings in. One prisoner, Roger Hayden, dons a golden mask and Diggle confronts him.
A woman, Nora Fries, is going through the supply room looking for her cyrostasis unit. Caitlin arrives and Nora says that she needs to find the unit. She releases a burst of frozen gas which hits Caitlin. Caitlin shrugs it off and transforms into Killer Frost.
Diggle takes on the prisoners, and Oliver arrives to superspeed them back to their cells and lock the doors.
More of the inmates make their way out onto the street, and Barry arrives with Cisco to take them out. Hayden--Psycho Pirate—hits Barry from behind and the van arriving to rescue Psycho Pirate hits Cisco. Kate, in her Batwoman costume, lands on top of the van and takes out the driver. When Psycho Pirate tries to run, Batwoman snags him and pulls him back. Barry and Cisco recover and Batwoman says that Kate told them to get out of Gotham and they should have listened to her.
Supergirl x-rays the asylum for the book.
Nora finds her husband's freeze gun and fires at Killer Frost. She calls for backup, and Barry goes to help her.
Deegan runs to a secret compartment and takes out the book. Supergirl arrives and blasts him back with her cold breath, then grabs the book. When she turns back to Deegan, she discovers that he's escaped.
Nora blasts Killer Frost unconscious, and Barry and Oliver arrive. Oliver throws a lightning bolt at her and it goes out of control, releasing stored gas vials. Malcolm steps out of the gas and tells Barry that no one is coming to save him, while Harrison Welles appears and tells Oliver that no one is coming to save him.
Caitlin wakes up to find Barry and Oliver fighting each other. She radios the others and says that they have a new problem. The heroes, meanwhile, imagine that they're fighting their villainous opponents, who are taunting them about how weak and slow they are. Batwoman arrives and takes them both down. She confirms that the gas is a hallucinogenic.
The group meets outside and wonders how the locked book changes reality. Batwoman is glad that they're leaving. Supergirl wishes her luck and says that her cousin is proud of him, and points out that she has x-ray vision. Batwoman deduces Supergirl's secret identity as well and they shake hands before Supergirl leaves.
Back at ARGUS, Felicity and the others go to work on opening the book. Barry talks to Oliver about how he's doing, noting what they saw back at Arkham. He wonders how Oliver lives with the burdens he carries, and Oliver tells him that he always thought Barry had it easy but assures him he can carry any burden thrown his way. Barry tells him not to wait to work things out with Felicity because they never know how long they have.
Oliver finds Felicity and talks to her privately. He tells her that they're going to be okay. Oliver says that people change and they're evolving, but he insists that his feelings for her won't change. He assures her that no matter who they are or what they become, she will always be the love of his life. They kiss, and a breach opens and the Earth-90 Flash arrives. The others come in and the Earth-90 Flash says that he's Barry Allen. He recognizes John but says that he's not wearing his ring, and explains that he traveled there to warn them about Mar Novu, who calls himself the Monitor and has been using the book--the Book of Destiny--to test multiple earths for the crisis that is coming. Novu thinks that the elseworlds the Book creates approximate the collision of Earths that they're facing. Cisco confirms brings up a news report showing Novu in the streets of Star City and recognizes him from the vibe.
The four heroes confront Novu and tell him to reverse the Book's effects. Novu refuses and when the Earth-90 Barry charges at him, Novu makes him vanish with a gesture. He says that a crisis is imminent and someone more powerful than himself is coming, and he's testing universes to find someone strong enough to stand against him. Novu admits that they are the first three he's tested who has recovered the Book. He teleports the Book to him, and Kara tries to attack Novu only for him to teleport her back.
Novu teleports to Deegan's lab and tells him to do better and think bigger. He gives him the Book and Deegan opens it.
Oliver and Barry find themselves in Central City in civilian outfits, and find a newspaper identifying them as the Trigger Twins. They realize that Deegan has rewritten reality again, just as the CCPD arrive and order them down on the ground. Barry and Oliver realize that they don’t have their powers, and Diaz is the policeman in charge and happily arrests Oliver. Oliver grabs him and shoots at the other cops, then knocks Diaz unconscious and runs off with Barry in tow. Superman flies down, wearing a black version of his original costume, and says that it's over for them.
Written by Gadfly on Dec 11, 2018