This review WILL CONTAIN SPOILERS for the episode to be discussed, if you do not want to have certain plot points or story spoilt, please do not read further.
After a couple of weeks off our screens and the shock reveal that Zoom is Jay Garrick/Zolomon Hunter, The Flash returned by introducing yet another speedster into the mix, Trajectory.
Some might think that it'd be a mistake adding another speedster to the show, especially as there are already two evil speedsters and one of those is still the big bad for the season, but Trajectory not only added a cool new rogue to the ever expanding gallery, but actually went a long way towards moving the Zoom storyline forward in an interesting way.
The episode opens with Barry in training for his upcoming fight to take down Zoom, with him trying and failing to reach enough speed to jump across a river. Frustrated that he can't seem to reach the speeds that Zoom possesses the team (minus Wells but including Jessie) decide to hit the town to get a little R&R. It's nice to see Jessie included in these scenes rather than being cooped up in Star labs still, with her not having an 'evil' counterpart on earth-1 like her father her not being allowed out of the labs felt a little strange.
As always the members of team Flash are much more interesting and fun to hang out with than those over on team Arrow, so watching them hang out in a nightclub is just as entertaining as watching them taking down a supervillain. We also had a fun moment as Barry introduces Wally to Jessie and tries to explain their awkward relationship. Also, did anyone else think that Jessie's metahuman watch going off around Wally might be hinting at the idea that he may already have powers of some kind? Maybe something that will allow him to copy Barry's speed for example?
Sadly for team Flash, they never get a night off, and the club is attacked by a red and yellow blur that steals everyone's money, the first introduction of Trajectory.
Despite the show already having two other superspeed villains Trajectory manages to stand out on her own and be different enough to be entertaining, and no, not just because she's a woman. Trajectory turns out to be a scientist, Eliza Harmon, working at Mercury Labs who had been helping Caitilin to develop the Velocity 9 speed formula.
Despite having only worked on a small part of the Velocity 9 formula Eliza was able to replicate the full thing and tested it out on herself. Whilst the formula did grant her super speed it also acted like a drug, not only making her crave more, but also damaging her psychologically to the point where she was developing a split personality.
It's this difference that sets her apart from Zoom and Reverse Flash, that Eliza is more of a victim of Velocity 9 than a bad guy doing evil for her own ends. She's essentially high when she's got her speed, and she's trying to make sure than she can have more Velocity 9.
Recognising that Eliza isn't a bad person Barry even tries to reach out to her in their final fight, to give her a chance to stop what she's doing. Sadly Eliza seems to be too far gone into her addiction and takes even more Velocity 9, before running so fast that her lightning turns blue and she appears to evaporate (my money is on her having either gone into the speed force or ran fast enough to travel between dimensions/in time).
During the course of the episode as Barry realises that he can't match Trajectory for speed he begins to question if taking Velocity 9 himself is worth taking the risk, despite knowing how dangerous it is. It shows Barry struggling between his desire to get faster in order to stop Zoom, but not wanting to break his own morals.
Luckily for him Harrison Wells is on hand to remind him that part of what makes someone a hero is their refusal to compromise and go against their morals in order to make things easier for himself. It's a powerful moment for Barry, and one that sets him on the right course, as well as reflecting the journey Harry has made since arriving on Earth-1 and the things he has had to do in the quest to try and get his daughter back.
During his final fight with Trajectory, though, Barry sees that Harry is right in his belief of him, as he manages to make an impossible jump that was even bigger than the one he failed to make at the start of the episode. Barry is learning to believe in himself and his own abilities and not to take the easy way out, even if it's for a good reason.
Trajectory's 'death' proved to be one of the more important parts of the episode, as it gave team Flash an important piece of the puzzle that is Zoom. Realising that it's Velocity 9 that causes speedsters to reach faster speeds than Barry, and turns their lightning blue Barry suspects a connection between Zoom and Jay.
When Cisco vibes whilst holding Jay's helmet he sees a vision that gives him the key piece of information that we the audience already have, that Jay and Zoom are the same person (or at least look the same). This revelation is sure to effect the team greatly, and makes the fight against Zoom a lot more personal for them.
'Trajectory' might be a villain of the week episode, but it gives the show an interesting and even sympathetic new villain (and one who looks great too) and manages to add a lot to the overall season long story with Zoom, with effects that are sure to be felt for the rest of the season.