- "I know you're here, Harrison Wells, and you did not come alone. You can try to hide... but I'm the fastest man alive. I will scour this city until I hunt you down. And when I do, all of you will feel my wrath."
- —Zoom's message to Harrison Wells
It acts as the second half of a two-part episode.
On Earth-2, the team races to find Zoom's lair and asks for help from the most unexpected source. Meanwhile, back on Earth-1, Caitlin rushes to perfect Velocity 9 so that Jay can stop the Geomancer.
Zoom realizes that Dr. Wells has returned to Earth-2 and issues a demand to the citizens of Central City to turn him in. Zoom attacks S.T.A.R. Labs looking for Wells and Cisco, but they manage to escape with the Earth-2 Barry. Wells, Cisco, and Barry update Iris on what happened with the Earth-1 Barry, so they all set out to find Killer Frost in the hope that she will lead them to Zoom. After a fight, Killer Frost agrees to take the team to Zoom. The team arrives to rescue Barry and Jesse, but Zoom shows up, too. The team is able to escape while Killer Frost keeps Zoom frozen and unable to move, but a third unidentified prisoner is left behind. On Earth-1, Caitlin creates "Velocity 9," a compound to temporarily give Jay his speed so that he can stop a new meta-human named Geomancer. After, Caitlin discovers that, when Jay uses Velocity 9, the serum starts to cure his illness. Jay, Caitlin, and Joe stabilize the breach and allow Barry, Cisco, Wells, and Jesse to return, but Zoom kills Jay and pulls him back through the closing breach to Earth-2.
- This is the first episode of the series to not feature Keiynan Lonsdale (Wally West) after signing on as a series regular.
- Cisco assures Harry he knew how to avoid being followed to S.T.A.R. Labs, citing that he's "seen Heat like, 50 times". He is possibly referencing the 1995 crime film Heat.
- The show that Earth-2 Barry describes, Commander Carl: Space Marshal of the Galaxy, is a reference to Commando Cody: Sky Marshal of the Universe.
- Patty Spivot is said to be a CSI tech on Earth-2 as she is in the comics. Though on Earth-2, she has already been a CSI tech for some time.
- This episode has Caitlin create the speed drug "Velocity 9". In the comics, this drug is created by Vandal Savage and gives The Flash enemy Inertia his powers.
- Cisco calls Killer Frost "Elsa", a reference to the protagonist of the movie Frozen, who has similar powers to Killer Frost.
- Cisco describes Zoom's lair at Ascension Cliffs to be like the Cliffs of Insanity. This is a reference to the cliffs in County Clare, Ireland, which have been used as filming locations for The Princess Bride and Harry Potter and the Half-Blood Prince.
- Earth-2 Barry and Iris say they have relatives in Atlantis and will go there to seek refuge from Zoom. Atlantis is home to one of the founding members of the Justice League, Arthur Curry aka Aquaman.
- The name of this episode is a reference to Escape from New York by John Carpenter. Like in the movie, Barry goes into a city full of enemies to rescue someone, and then has to escape the city full of villains who are trying to stop him, similar to the movie's main character, Snake Plissken.
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