13. Welcome to Earth-2

In Earth-1, Barry Allen closes all of the breaches leading to parallel universe Earth-2, except for the one in S.T.A.R. Labs. Using the last breach, he travels to Earth-2 with Cisco Ramon and Harry Wells to rescue Harry's daughter Jesse, who has been kidnapped by speedster Zoom. However, an energy surge destabilizes the breach, leaving the trio stuck on Earth-2. After seeing his doppelgänger, a non-metahuman forensic scientist, on the news, Barry abducts and renders him unconscious to impersonate him and obtain more information on Zoom. He meets this Earth's Iris West, who works as a police detective and is married to his doppelgänger.

Earth-2's versions of Caitlin Snow and Ronnie Raymond, known as Killer Frost and Deathstorm respectively, are working for Zoom and realize that some breachers have entered Earth-2. Barry and Iris meet Joe West 's doppelgänger Joseph, a lounge singer. Frost and Deathstorm find and attack Barry at the lounge; Deathstorm fatally wounds Joseph during the attack. Barry fights Frost and Deathstorm outside; the two metahumans escape after Frost is injured.

Meanwhile, a metahuman named Adam Fells / Geomancer appears in Earth-1 Central City. Joe suggests that Jay Garrick use the serum Velocity-6 to fight Fells. Jay refuses and reveals to Caitlin that he invented Velocity-6 and previously took it to become faster but the side effects caused his loss of speed and are gradually killing him. Caitlin develops Velocity-7, which Jay uses to engage Fells until it wears off. Fells almost kills Jay until Joe shoots at him, and escapes.

Back on Earth-2, Iris, her partner Floyd Lawton and Cisco confront Frost and Deathstorm. Cisco, who has made a weapon to combat Frost, attempts to stop the pair, but is confronted by his own doppelgänger, known as Reverb, who is also working for Zoom and can manipulate sonic vibrations to create powerful shock waves. Cisco calls for Barry, who arrives and uses Cisco's weapon to wound Frost, but is stopped by Reverb and Deathstorm. They use their powers repeatedly on him, despite Frost's objections and Zoom wanting Barry unharmed. Zoom arrives, kills Reverb and Deathstorm for harming Barry, captures him and speeds away. Barry later awakens in a glass cell at Zoom's lair, where there are two other prisoners; Jesse and a man trapped in an iron mask.