The Flash season 2, episode 17, “Flash Back,” features Barry traveling back in time to find a way to get faster.
In the final moments of the previous episode, the S.T.A.R. Labs team realized that Jay is actually Zoom. This is a huge betrayal for everyone, but especially Barry and Caitlin. With all the breaches to Earth-2 closed, however, Barry will need to find another way to reach Earth-2 in order to confront Zoom.
The synopsis for The Flash season 2, episode 17, “Flash Back,” reads:
“A MOMENT IN TIME GETS BARRY ONE STEP CLOSER TO ZOOM; ANDY MIENTUS RETURNS AS HARTLEY RATHAWAY — After the shocking revelation that Zoom is Jay Garrick (Teddy Sears), Barry (Grant Gustin) is more determined than ever to get back to Earth-2 to stop Zoom forever. Desperate to find a way to increase his speed, Barry decides to travel back in time and masquerade as his earlier self in order to get his arch-nemesis, Dr. Harrison Wells/Eobard Thawne (Tom Cavanagh), to teach him how to run faster. However, things don’t go as planned and Barry is stunned to face familiar foe Hartley Rathaway (guest star Andy Mientus), as well as old friend Eddie Thawne (guest star Rick Cosnett). Iris (Candice Patton) makes peace with her past in order to embrace her future. Alice Troughton directed the episode penned by Aaron Helbing and Todd Helbing (#217).”
Based on this synopsis, it looks like Barry will travel back to season 1, episode 11, “The Sound and the Fury,” when the team confronts Harrison Wells’ former protege, Hartley Rathaway. It will also be interesting to see the present day Barry confronting Eobard Thawne-as-Harrison Wells, knowing who he is while pretending not to.
I’m not even going to try to wrap my head around the time travel rules before the episode airs and just hope they give us a good explanation for how things have worked out for the timeline.
We also know from EP Greg Berlanti that this episode will show how Barry got to Supergirl on Monday’s crossover as well as what happens after he gets back:
For the sake of the crossover, Supergirl and The Flash “flip order because [Supergirl] airs on Monday, and The Flash episode that hints at how he gets over there and gets back airs on Tuesday. The audience will have to forgive us that one is going to air before the other, and they shouldn’t wait to watch Supergirl until after The Flash episode. But, you’ll see the shout-out in the next episode of The Flash. It deals with Barry increasing his speed. I’m very excited about the next episode of The Flash, too.”
Finally, watch a trailer for the episode:
