Over a thousand-foot cliff, Team Flash try to get Barry’s speed up in a dangerous test. While everyone’s ambivalent about Barry running across one thousand feet of air, Barry insists that he needs to get faster to stop Zoom. He begins his run and makes it nearly halfway across the cliff before he falls. Fortunately, Cisco rigged up drones with a safety net to save the speedster.
Back at the base, where they now keep Jay’s helmet in a place of honor, Jesse sees the team return while being confused at Senator Knowles being a popstar. Barry is still frustrated at being unable to cross the cliff and wants to continue tests. Cisco, however, suggests that they take a break to recuperate by going out to a club, a suggestion that Caitlin actually agrees to trying. Jesse asks Harry for permission to go, but Harry initially rejects it. Jesse argues that he wanted her to be more active in the new world and get to know the team, along with the fact that Zoom is in an alternate universe. Harry then agrees, so long as she takes metahuman watch for protection.
Barry, Cisco, Caitlin, and Jesse go to a local club where they toast to Jay (until Barry points out that Jesse’s underaged). The group run into Iris and Wally, who’s equally out of place in the club that Barry picked. Barry then admits that he doesn’t know much about clubs, only that this place got four stars on Yelp. Jesse meets Wally, with the two unexpectedly hitting it off until Jesse’s watch beeps erratically. She goes to the bathroom to turn it off, only to come across a secret recording from Harry after killing the Turtle. Cisco then offers to dance with Caitlin which turns into wild moves on the dance floors. Alone with Barry, Iris notes how odd it is that they’re married both in the future and on Earth-2. Before they can discuss further, however, a burst of lightning bolts through the club and steals everyone’s wallets just like the Flash. Barry attempts to chase after the new speedster but finds himself unable to keep up the chase.
Joe arrives at the scene of the crime where they try to figure what happened. Iris, unfortunately, finds that a woman had taken a picture of the blur looking similarly to the Flash, something her new boss Scott is anxious to exploit. Iris tries to argue against the Flash being a petty criminal, but Scott insists on a new article tomorrow. Back at STAR Labs, Jesse confronts Harry on his desperation to rescue her leading to being a killer, but Harry doesn’t deny his fear of losing her to Zoom. The team try to discover the origins of the new speedster when Caitlin reveals the creation of the Velocity-9. While it creates super speed, it has devastating effects in cellular degeneration. Barry is frustrated that another way to gain speed exists, but Caitlin insists that she cannot find a cure for the effects. Cisco touches Caitlin but then receives a vibe seeing Zoom on Earth-2. Before he can explain it, the team is alerted to the new speedster’s presence downtown, and Barry races to find her.
The speedster causes chaos down the streets while Barry attempts to slow it down. After colliding, Barry discovers that the speedster is, in fact, a woman. Cisco’s surprised at the existence of a lady speedster and wonders how she looked (for science). Her identity is still unknown, but, from noticing that her suit was made from the same material as the Flash, the team deduce that she must have access to some lab. Caitlin recalls a colleague from Mercury Labs who helped her fill in some holes for the structure of Velocity-9 name Eliza Harmon. Harry notes that with the few details she had, Eliza could always reverse-engineer her own formula, but Caitlin believes that it would be out of character for her. Caitlin and Joe decide to see for themselves.
At Mercury Labs, Caitlin meets up with Eliza who appears friendly though addicted to work. Caitlin admits that she came to question her regarding a new speedster and the drug they worked on together. Eliza believes that it couldn’t have come from this lab but that security has been laxed since Mcgee’s kidnapping. While she doesn’t offer any leads, she offers any kind of help as a friend to Caitlin. Meanwhile, Iris has been putting off her article by stating that she knows for a fact that the speedster was not the Flash, but, without a valid source, Scott refuses to let her run that angle. In order to distract from smearing the Flash, Iris offers to go with Scott to get some coffee which he accepts.
At Mercury Labs, Eliza overworks herself, complaining that she’s six months behind in her work despite the drug’s effects. A voice remarks behind her that it’s only because she’s a perfectionist and refuses to revel in chaos. Eliza notes that it’s all her fault for getting them hooked on the drug in the first place, but the voice states the Caitlin was the one who left the formula out in the open for them to take. Against Eliza’s better judgement, she takes the remaining vial of her Velocity-9, revealing herself to be the female speedster with a new plan on how to get more.
Barry and Harry talk about Barry’s training where Barry once again suggests taking the Velocity-9 to level the playing field against other speedsters. Harry states that every time he compromises his values he loses a piece of his humanity, and taking the Velocity-9 is a great risk. Harry remarks that Barry should try to emulate Jay who worked for his speed. Suddenly, STAR Labs is infiltrated by the female speedster who locks the Flash in the pipeline. She then knocks Joe aside and takes his gun. She calls herself Trajectory and demands that Caitlin hand over a case of Velocity-9. In the chaos, Cisco gets another vision of Zoom, but Trajectory is adamant and threatens to kill them one by one starting with Jesse. Harry states that they will make some for her.
At Jitters’, Iris and Scott talk about the Flash, whom Iris considers a hero, but Scott looks with scrutiny. He tells a story of writing a story about a corrupt mayor who had the city’s support but had a campaign bought and paid for by the mob. He states that their jobs as reporters is to report on the truth, and even heroes are held accountable, remarking that this must be a turnoff for the people she dates. Iris, however, says this isn’t a date, leading Scott to understand that she just wanted to distract him from posting the article. Iris apologizes, but Scott tells her to save it.
Harry and Caitlin complete a vial of Velocity-9, but Trajectory doesn’t trust the scientists. She then sticks Jesse with the formula to prove its worth and steals the rest when Jesse survives. However, after Trajectory leaves, Jesse collapses in a seizure from the drug. Caitlin states that a blood transfusion will flush the drug from her system with Harry being a perfect match in PZ Negative, which Cisco notes is not a thing on this earth. Jesse survives the drug, but she still expresses mistrust in her father willing to give Trajectory everything she wanted just to save her.
Caitlin reveals that she placed a tracker in the drug to find her moving back and forth on a city bridge. Barry deduces that Trajectory is building up enough friction to destroy the bridge and everyone on it. Barry runs to find the bridge collapsing beneath the people. He manages to rescue the 200 people on them but still has to fight Trajectory. When the bridge collapses, he has no choice but to make the jump at Mach 3.3, a feat he finally accomplishes. He tries to stop Trajectory to appeal to Eliza, but she takes the drug anyway. When she attempts to run away, however, her lightning turns blue and causes her to evaporate into thin air.
Iris reveals to Scott her new article about the Flash stopping Trajectory, stating that it was easier to write the truth. She also remarks that after getting over the initial surprise, she wouldn’t be opposed to a date with him, much to his pleasure. At STAR Labs, Harry finds Jesse’s watch where she recorded a message stating that she has left on her own to discover what the world can offer in Opal City. Barry reveals to the others on Eliza’s blue lighting comparing it to Zoom. Harry believes that Zoom, too, is dying and requires a cure from the Velocity-9, just like Jay. Cisco then reveals his vibes about Zoom coming from Jay’s helmet, discovering for themselves that Jay is really Zoom.
- "Yeah, I picked it. I don’t go out much. It had four stars on Yelp." -Barry
- “I wonder what our married doppelgangers are doing right now?” -Barry “Probably the Earth-2 equivalent of Netflix and chill.” -Iris
- “Wow, how very Law and Order of you, Caitlin.” -Eliza
- “Villains gonna vill.” -Cisco