The Flash - 'Trajectory'

I'm sure at high enough speeds, that hair would channel the air and make her
spin.

The Flash's reputation is in trouble as a new speedster appears and begins doing crimes; and she's even faster than he is. Caitlin realises that they might have been empowered by the highly dangerous Velocity 9 she developed for Jay, and that this lady speedster (Cisco is very excited at the prospect) may be a former colleague from Mercury Labs, Eliza Harmon. Meanwhile Iris is being pushed by her editor, Hipster McHatesflash, to write a hatchet piece on the Flash's turn to crime (as all anyone sees is Speed Force lightning.)

Although initially deflecting suspicion, Eliza is the speedster, suffering from a kind of split personality and calling her speedster self Trajectory (Cisco mourns that the crazy ones always name themselves.) She traps Barry in the Pipeline and forces Caitlin and Harry to mix more V9, which she tests on Jesse, nearly killing her. Harry gives a transfusion to flush out the drug, but Jesse also knows that he killed the Turtle. Rejecting his claim that he has to protect her while the world looks out for itself, she leaves town, but that's later.

Talked out of using V9 on himself (by Harry, who convinces him that 'cheating' would make Barry like Harry, which is not something that he wants,) Barry has to push his sped to the limit to take down Trajectory. As her Speed Force falters, Barry tries to get through to Eliza, offering to help her, but her addiction wins out. She shoots herself full of V9 and flees, her lightning turning blue, but before she gets far her body seems to atomise.

Barry speculates that Velocity may have created Zoom's powers, and notes that Jay was known to use Velocity. When Cisco admits he has been vibing Zoom, Barry breaks Jay's helmet out of its case. Cisco vibes it and sees that Zoom is Jay.

Oh, and Iris and Hipster McHatesflash have a heart to heart about fallen heroes and maybe there's a thing there. I... actually don't care.

As to Zoom, I am starting to suspect that Zoom is more like Eliza's evil Trajectory self (an aspect Team Flash knew nothing about;) a Speed Force doppelganger created by the Velocity, who perhaps doesn't want Barry's Speed to fix genetic damage, but rather as sustenance. I wonder if the Jay the team knew was the original that Zoom escaped from, or perhaps if that was iron mask Jay?

It was a shame to see the end of Eliza Harmon so fast - although as I understand it, this is par for the course for the character - when there was potential to explore the corruption of power as well as the nature of Velocity, although if Zoom is disembodied Speed Force, it's possible that Trajectory actually dissolved into Speed and is still around somewhere.