[WARNING: This article contains SPOILERS for The Flash Season 2, Episode 17.]

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Following the unmasking of Barry Allen's (Grant Gustin) season 2 foe Zoom and the revelation of his connection to Jay Garrick (Teddy Sears), The Flash took a short break only to return with somewhat of a filler episode in 'Trajectory', which at least served the purpose of showing Barry and the other members of the S.T.A.R. Labs team getting up to speed on Zoom's identity. This week, The Flash delivered a complete bottle episode before heading into another break in the show's second season.

In 'Flash Back', directed by Alice Troughton and written by Aaron Helbing and Todd Helbing, Barry travels back in time a year to the events of the season 1 episode 'The Sound and the Fury'. There, he attempts to infiltrate the S.T.A.R. Labs team of that time by posing as his younger self in order to glean information from Harrison Wells/Eobard Thawne (Tom Cavanagh) about how to increase his speed. However, when a Time Wraith appears with Barry in the past, he ends up somewhat altering the future and brings home some emotional closure for Iris (Candice Patton) in the form of a video message from Eddie Thawne (guest star Rick Cosnett).

If Barry Could Turn Back Time...

As the series showcased in season 1, The Flash manages to deliver surprising and, for the most part, earned reveals in the main ongoing mystery, but can feel a bit meandering in the episodes following these revelations. 'Flash Back' is another case of ostensibly dedicating an episode to the larger season arc - in this case, Barry's determination to increase his speed in order to face Zoom - while actually spending much of the episode's runtime on a self-contained storyline: Barry's disruption of the S.T.A.R. Labs' fight with Hartley Rathaway (guest star Andy Mientus) and the appearance of the Time Wraith.

Despite a montage study session he attends with his time's Caitlin (Danielle Panabaker) and Cisco (Carlos Valdes) to prevent such a thing from happening, Barry's disruption of the timeline feels inevitable, especially when he arrives earlier than planned in the past. But, though this change in timeline offers a fresh take on the events of 'The Sound and the Fury' - especially providing an exciting, if too short, fight sequence between Barry's past and future selves - it hardly feels necessary to rewrite Hartley from a villain to a hero. That is, until it's revealed when Barry returns to his own time that Hartley is the only member of the S.T.A.R. Labs team capable of creating a device that can destroy the Time Wraith - which forces the viewer to presume Caitlin and Cisco couldn't have figured it out on their own, a notion contradictory to everything we've seen on The Flash so far.

As for Hartley, because of Barry's meddling with the timeline, the Pied Piper is now part of the S.T.A.R. Labs team, presumably with the past year of The Flash rewritten to include him as a hero rather than a villain - similar to how Buffy the Vampire Slayer inserted Dawn into the show at the end of season 4. But, with little time spent back in the future at the end of 'Flash Back', Hartley's appearance in S.T.A.R. Labs is largely left unresolved - a strange occurrence for a show that has previously explored the consequences of altering the past in depth.

As far as justification goes for the storyline of 'Flash Back', it largely comes from Gustin's portrayal of a Barry who is desperate to save his friends and family from Zoom. This certainly isn't the first instance of The Flash relying on Gustin's acting capabilities to pull off a more unbelievable story development, and it surely won't be the last. But, to Gustin and Cavanagh's credit, both make Barry's trip to the past worthwhile.

Within the confines of 'Flash Back', viewers are given a chance to see the enemies interact on a new playing field, one where Eobard doesn't necessarily have the upper hand. Their tense standoff in the Time Vault especially, where Barry finally finds himself to be evenly matched with Thawne, offers a new emotional resolution to their mentorship-gone-wrong that may have been lacking following Thawne's death at the end of season 1.

Additionally in the episode, Barry takes a break from being the mentee to take on the role of a mentor to his younger self and the younger versions of Caitlin and Cisco - a theme carried over from the crossover episode with Supergirl. While this aspect of 'Flash Back' gives viewers a fresh look at these characters, the episode still falls into the meandering mentality the show can take on after one of its big reveals.

A Message From Eddie

One of the stranger aspects of 'Flash Back' is the episode's choice to double down on the C-plot of 'Trajectory' and deal with Iris opening herself up to the possibility of a new relationship. The misunderstanding between Iris and her new boss at CCPN, Scott Evans (Tone Bell), was handled, at best, haphazardly in 'Trajectory', and 'Flash Back' continues Iris' emotional development by having her and Barry discuss whether she's ready to pursue a new relationship - presumably with her boss. Although 'Flash Back' attempts to give Iris some resolution to her relationship with Eddie, the story thread is built out of the strange plot of 'Trajectory' and will likely service a romantic relationship between Iris and her boss.

Still, since Barry traveled back a year to a point in time when Eddie was alive and he and Iris were still together, it gave both Barry and Iris the opportunity for closure. Additionally, Cosnett's delivery of Eddie's message to Iris helps to bring this emotional storyline together, even as it showcases that most of Iris' development, especially in season 1, largely hinged on her relationships with either Eddie or Barry. As Iris' relationships with her father Joe (Jesse L. Martin) and newfound brother Wally (Keiynan Lonsdale) have progressed in season 2, this particular return feels like too much of a step back for her character. We can only hope that The Flash will use Iris' closure when it comes to her relationship with Eddie as a stepping stone for something new, though it remains to be seen if that will be the case.

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'Flash Back' is a space-filling bottle episode if The Flash ever had one, but the show manages to pull out enough compelling character moments and exciting match-ups to make this particular hour of television enjoyable for the most part. Still, with the revelation of Zoom's identity in the rearview mirror and Barry anticipating a massive fight with his season 2 enemy, The Flash's more exciting season 2 moments are ahead of us.

Next: Zoom's True Identity - What Does It Mean?

The Flash continues with 'Versus Zoom' on Tuesday April 19th at 8pm on The CW. Check out a preview below: