The sun is setting on Season 2 of The Flash. There are only a few episodes left until Barry (Grant Gustin) at last confronts Zoom (Teddy Sears). But if the trailers are any indication, their showdown will come sooner than the May 24 season finale. Before Barry can go to war with Zoom, he needs to get faster and “Flash Back” has Barry running all the way back to the bygone days of … Season 1, right into the episode “The Sound and the Fury.”

Desperate to improve his speed, Barry has a revelation thanks to Wally West (Keiynan Lonsdale). He goes back to in time to seek help from the Reverse-Flash, Eobard Thawne, then disguised as Harrison Wells (Tom Cavanaugh). Get his MacGuffin (a key speed formula) without disrupting the timeline, and no one will be the wiser. And since it’s such a highly delicate operation, of course it all goes wrong, especially when a Time Wraith is hot on Barry’s heels.

The Time Wraiths, according to Eobard, are ghostly apparitions that patrol speedsters from traveling in time, which Barry has only been lucky to have avoided in his own travels, thus far. (Also, don’t get it confused with Wraith, the U.S. government’s own super alien they’ve employed since World War II.)

This doesn’t seem to be a move planned long in advance. Nothing in the season 1 episode “The Sound and the Fury” predicted this would happen. Season 1 Barry doesn’t see Season 2 Barry, and pretty much all of “The Sound and the Fury” gets overwritten after Barry meddles with the timeline. The show’s production did a stellar job recreating Flash’s battle with Haw Pied Piper (guest star Andy Mientus reprising his role), which fooled even me.

In the grand scheme, “Flash Back” is a fun reward for longtime viewers — and it doesn’t delve too much into the show’s own substantial mythology. There’s not many worthy callbacks to anyone who’s been around since day one, just the pleasure of seeing old faces (Rick Cosnett returns as the doomed Eddie Thawne) and even Barry’s interference to the timeline isn’t dramatically severe — if anything, it’s a happy one, with Hartley the Pied Piper having a repaired relationship with his parents and the rest of S.T.A.R. Labs.

Barry obtained the formula from Eobard. That’s all that matters now, and whether or not it will actually work when Barry can finally run circles around Zoom. It’s going to be one hell of a fight.

Photos via The CW