At S.T.A.R. Labs, Harry records a journal entry, about how he has become distracted by the people he has met on Earth-1. But he never forgot Jesse and is coming for her. And he is not coming alone. While he does this, The Flash closes all of the breaches, except for the one in S.T.A.R. Labs.
Barry has a sort of goodbye dinner with Joe and Iris before heading to Earth-2. Barry admits that he never told his father what he was doing, he worried Henry would talk him out of it. When they are alone, Iris asks Barry if he is doing this because he thinks there is nothing left for him on Earth-1. He assures her that while he misses Patty, he loves his life. Iris tells Barry to win, and come home.
At S.T.A.R. Labs, Jay lectures Barry and Cisco that everything they see will be weird and wrong, they should not get personally involved. Barry tells Jay that if they aren’t back in 48 hours, it means Zoom won and they should close the breach. Cisco gives Caitlin a letter to give his family if he doesn’t make it. Everyone says goodbye, even Joe and Harry. With one more warning about not getting distracted, Jay powers up the speed cannon. Barry grabs Harry and Cisco and they go into the breach.
In the breach, flashes of images, including Supergirl and another Flash appear.
A piece of the speed cannon breaks off, and Jay saves Caitlin from being crushed by it. Jay realizes that with the other breaches closed, this one is less stable. The others might be trapped on Earth-2.
After seeing a few more images in the breach (including Gorilla Grodd) they arrive on Earth-2. The city practically shines, with technology far beyond that on Earth-1, yet a style of clothing, cars, and décor that is from decades past. Cisco and Barry are stunned by everything they see, including a very kind, normal Henry Hewitt working at S.T.A.R. Labs.
Harry brings Cisco and Barry to his office, where the news shows that things are worse since Harry left. Mayor Snart has issued a curfew to protect the citizens from Zoom. Cisco puts on his glasses, trying to vibe on Zoom. When it doesn’t work, they realize that this world’s frequencies are different and the glasses won’t work. At that moment, Barry’s Earth-2 double appears on the news, talking about Detective West’s work against Zoom. He’s also a CSI, though he wears glasses and dresses very differently than Barry. Barry speeds off and returns right away with his double. The Earth-2 Barry is freaked out by being abducted by his own metahuman double, but also starstruck at meeting Harry. Barry renders his double unconscious in order to take his place, and find out what the police know about Zoom.
At CCPD, Barry is shocked to see Singh is not a police officer, but a criminal being arrested. Furthermore, Floyd Lawton is a cop, and apparently the worst shot on the force. The nickname Deadshot is still used, only sarcastically. It also turns out that Detective West is Iris, not Joe.
Iris brings Barry into a hallway and begins kissing him. He’s shocked, but quickly learns that Iris and his double are married. Iris is surprised that her metahuman detector is going off, but assumes it is broken.
A group of men who stole a few million dollars are attacked by a minion of Zoom’s. She is revealed to be Caitlin, only she is a metahuman known as Killer Frost. She kills two thieves, stabbing one with icicles and freezing another while kissing him. She is joined by Ronnie, who has Firestorm’s powers, but goes by the name Deathstorm. He tells Killer Frost that some breachers crossed over, and she is thrilled at the possibility of killing them.
Iris and Barry go into their home, and when he turns away while she undresses, she asks what’s wrong. He evades, and she tells him that his mother called. Stunned, Barry moves to the phone, and sees a button labeled Mom and Dad. He pushes it, and Nora Allen answers the phone, thanking him for the anniversary gift he gave her and Henry. Barry cries silently as he talks to his Mom.
In Harry’s office, Harry is stressing about not hearing from Barry. Cisco isn’t worried, he’s more curious about who he is on Earth-2. Harry tells Cisco to focus on finding Zoom.
Jitters is Jitterbug on Earth-2, and apparently Joe is the headliner, he’s singing when Iris and Barry walk in. After the song, Joe greets his daughter warmly, and his son-in-law coldly. Insisting on Barry calling him Joseph (and calling Barry Bartholomew) it is clear that Joseph does not like Barry Allen at all. He blames Barry for Iris becoming a cop to pay for his education. Iris reminds Joe that she loves being a cop and it was her choice.
Jay works on repairing the speed cannon with Caitlin’s help. Joe is there as well, there is a new metahuman in town, causing earthquakes. Jay recognizes him from Earth-2, his name is Adam Fells and he calls himself Geomancer. Joe suggests Jay use Velocity-6 to help fight Geomancer. Jay is unwilling, and Joe reminds him that Barry is saving Earth-2, and Earth-1 needs a Flash. Once they are alone, Jay admits to Caitlin that he took Velocity-6 before, to get faster. The side effects are why he lost his speed, and the cause of the illness that is killing him. Caitlin offers her help.
At Jitterbug, Joseph starts a new song. But he is interrupted by a number of metahuman detectors going off, right before Killerfrost and Deathstorm enter. They search for the breacher, and right as they become suspicious of Barry, Iris draws her gun. All the civilians, beside Barry and Joseph, run out. Barry tries to talk Killer Frost down, calling her Caitlin. She hates that name, and they attack. Trying to protect Iris, Joseph takes a direct hit of fire from Deathstorm. Barry speeds Killer Frost and Deathstorm outside. Deathstorm flies after Barry, shooting fire at him. Barry speeds to a statue of Jay as the Flash and pulls off the helmet, using it as a shield. He deflects a fireball into Killer Frost, and she is hurt. She and Deathstorm escape.
In Harry’s office, Harry and Barry fight angrily. Harry wants them to focus on Zoom, these people are not Barry’s Joe and Iris. Barry insists that they are still his family and they need him.
Joe tracks down Geomancer just as Wally shows up. Before they can talk, a new tremor shakes the CCPD, and Joe takes off to get Geomancer.
In Barry and Iris sit by Joseph’s hospital bed. He tells his daughter that before every sing, he tells himself the same thing. “This one is for Iris. My baby girl. Every song is for you.” Joseph tells Barry to take care of Iris. He dies.
At CCPD, Lawton insists on joining his partner Iris on her search for Deathstorm and Killer Frost, even as he scrambles to pick up the bullets he dropped. Barry shows, with Cisco, who has made a weapon which might work against Killer Frost. Iris refuses to let Barry join them, but reluctantly lets Cisco, since he is the only one who can use the weapon.
Joe faces off with Geomancer, who thinks The Flash is gone. Jay speeds onto the scene, in his Flash outfit. Jay and Geomancer fight, until the Velocity-7 Caitlin created wears off and Jay takes a bad fall. Geomancer grabs Jay’s head, threatening to use his powers on Jay’s head. Before he can, Joe shoot at him and Geomancer escapes.
Iris, Lawton, and Cisco arrive in an alley, where a snitch sent them. Killer Frost and Deathstorm are there, and they force the cops to lower their weapons. Cisco hides his in his pocket and asks Deathstorm about Martin Stein. Deathstorm admits Martin has been trapped inside him for years. Suddenly, someone else appears, claiming that Killer Frost and Deathstorm work for him, and he works for Zoom. The person walks out of the shadows. He is Cisco’s double.
Cisco and his double face off. Cisco introduces himself as Vibe, and the double uses the name Reverb. Reverb has the same powers as Cisco, but much more control and ability. Reverb wants to train Cisco to be like him. There is much more to his powers, and they could be gods. Cisco responds by calling to The Flash for help.
The Flash speeds in, and uses Cisco’s weapon to wound Killer Frost. Cisco and Reverb continue to face off. Lawton tries to shoot Reverb, and misses every shot. Using his powers, Reverb hits Lawton with a huge vibration. Deathstorm and Reverb both use their powers repeatedly on The Flash. Killer Frost yells for them to stop, Zoom wants him unharmed. Zoom shows at that moment, and kills Deathstorm and Reverb to punish them. He chokes Killer Frost, but lets her live before capturing Barry and speeding away.
Caitlin tends to Jay’s wounds. Velocity-7 worked pretty well. She is sure Velocity-8 will be even better.
Barry wakes in a glass cell. There are two other prisoners there, someone in a metal helmet and Jesse. He tries to reassure her, but Zoom faces off with Barry through the glass, taunting him.