The Flash had to deal with change during last night's episode

Last night's episode of The Flash was transitional, signaling that the show may be headed into the final story arc of its second season. What that means for Barry Allen (Grant Gustin) is anyone's guess though because last night he decided to play with time travel, and it didn't end well.

Allen continues to be frustrated that he can't raise his speed to the level of Zoom or Reverse Flash. Performing a high-speed analysis, Dr. Caitlin Snow (Danielle Panabaker) determines that all three speedsters move their limbs at the same speed. However, Reverse Flash and Zoom's feet maintain more contact with the ground thereby giving them more thrust. It's got everyone stumped.

To crack the code, Allen makes a bold decision. He'll go back in time, impersonate himself and dupe the old Dr. Harrison Wells (Tom Cavanagh), a.k.a. Eobard Thawne, into teaching him the secret. Before he leaves, though, Earth 2 Harrison Wells has some advice. Er, well ... commentary, rather.

"Your plan is asinine," Wells says, before issuing an ominous warning. "I promise you when you come back things will be different. And only you will know what those differences are."

But Allen shrugs it off, packs a bag, hops inside the particle accelerator and takes off into the past.

Unfortunately Allen missed his mark.

The goal was to re-enter the time stream at a point where he was alone and defenseless. Instead, he lands right in the middle of his very public battle with Hartley Rathaway (Andy Mientus), a.k.a. the Pied Piper. (If you're keeping score at home, that's episode 11 of season one.) What follows is a funny little bit where Allen plucks himself out of the fight, pulls himself around the corner into an alley and puts himself to sleep.

As an aside, if you ever travel back in time and have to knock yourself out at least have the common decency not to just leave your own unconscious body passed out in an alley for six hours. That's just rude.

Anyway, things are going well up until the point where Allen actually opens his mouth to speak words.

Thawne immediately becomes suspicious. His Barry Allen is a snot nosed punk kid without a brain in his head. This Barry Allen simply knows too much about the speedforce, about physics and about ... him. So he sucker punches him from behind, drags him into his secret room and handcuffs him to his wheelchair. That thing must weigh a ton, because for all intents and purposes Allen acts like it's the end of the line for him and tells Thawne everything.

But rather than kill the boy right there, Thawne is consumed with a bigger problem. It seems that a time wraith — a legless, flying, ghost-like apparition — has followed Allen through the breach and is bent on his destruction.

What is a time wraith? No one knows, not even Thawne. We just know that they hate it when speedsters manipulate the timeline. And they're indestructible.

From there, the rest of the episode is a bit of a wash. Thawne and Allen are at a loggerhead. Thawne wants the time wraith gone, and Allen wants the secret to running faster. So eventually Thawne gives up the details to something called "tachyon enhancement" on a blinking blue flash drive and Allen runs off to his future with the time wraith hot on his heels.

But before he goes, Allen whispers to Cisco Ramon (Carlos Valdes) hat the moment he arrives he'll need some specialized tech to defeat the time wraith. That gives STAR Labs' resident gearhead a few years to build a gadget and, sure enough, when Allen arrives on his side of the breach Cisco has a funky new pistol in his hands.

But it doesn't work. The time wraith keeps coming, grabs Allen by the neck and begins to turn him gray and ashen. Before long, Allen looks just like the time wraith.

It's at that moment that Rathaway leaps out of the shadows, aims his sonic gauntlets at the wraith and turns him to dust. It seems that in going back in time Allen has changed his reality. Instead of being an enemy, Hartley is now an ally.

But Allen succeeds in bringing back the secret of tachyon enhancement. He has what he needs to beat Zoom. We'll just have to wait and find out what else has changed about his timeline and exactly what kind of wrench it throws in the works.