Spoilers for The Flash included.
This is The Flash.
Barry gives a voice-over about trusting someone he shouldn't have. Again. Just like he trusted Harrison Wells, who turned out to be Eobard Thawne and the Reverse-Flash, he trusted Jay Garrick, who is Zoom. He had wanted them to help him become better, but they were both only looking to use him for their own gain. Now he's determined to learn to run faster in order to stop Zoom. As Team Flash uses science to increase Barry's speed, Cisco vibes again. This time he sees Zoom holding someone--Iris?--over the edge of a building. (Uh-oh. Not good.) Then, Caitlin asks the impossible question: What if Barry can't run faster than Zoom? (Duh-duh-DUN!)
The Wests meet at home for dinner. Joe and Iris reassure Barry that nothing related to Jay or Zoom is his fault; nobody could have predicted that could happen. (Only a number of Flash fans posting on the Internet.) While Joe grabs the food, Iris tells Barry about her date with Scott. She says it doesn't feel right because it reminds her too much of Eddie. (Poor Iris.) Barry encourages her to move forward. Wally shows up and tells them about his new project. He's reading up on old journals of inventors to help push speed limits or something. (You know, science.) But this gives Barry an idea.
He decides in order to get faster he has to learn from someone who was able to manipulate the speed equation. That someone would be none other than Harrison Wells, or Eobard Thawne. He wants to travel back in time to last year and get him to teach him to run faster. Harry is completely against the idea, mentioning that it will alter the timeline, that Wells will know that Barry isn't who he says he is. But Barry points out that if he doesn't stop Zoom, it won't matter anyways--nobody will be safe. So Cisco and Caitlin help him pick a specific time frame from last year to travel to.
Barry time travels, but in the time vortex a creepy Dementor thing comes at him and messes up his travel. He arrives a little too early in the timeline. His past self is facing off against the Piped Piper, Hartley Rathaway. (You know, the guy with the crazy gauntlets that let off that awful frequency.) Barry grabs his past self and tries to knock him out, but it doesn't work exactly as planned. He has to chase his past self down and inject him; it's kind of a really cool moment in the episode with the lightning speed zipping all over. But he manages to knock his past self out and switch the lightning bolt logo. He then stops Hartley (which is not what happens originally) and takes him to STAR Labs.
At STAR Labs, he asks Wells about the speed equation. Wells obviously knows something is up with Barry, but he does help him out. At the same time, Eddie is still alive (Oh...), and Joe asks him to help out with investigating Wells. But before they can leave, the creepy Dementor attacks the CCPD building. STAR Labs gets an alert, and Barry tries to brush it off as nothing. Wells urges him to go help out, so he does. But by the time he gets to the CCPD, the Dementor has vanished, and he sees Eddie.
Barry, Joe, and Eddie meet in the forensics lab (where the Dementor was originally sighted). Joe asks Barry why he's acting so weird about Eddie, but Barry brushes it off. He returns to STAR Labs, where Wells seems to be waiting for him. Cisco and Caitlin are trying to track the Dementor, so Wells asks to talk to Barry privately. Once they're alone, Wells stands up and knocks Barry out. Barry wakes up in Wells' super secret room, strapped to the wheelchair. Wells talks to him, explaining that the Dementor is a "Time-wraith," which go after people who travel through time and don't know what they're doing. (Okay, but let's just take a moment to appreciate this cast's acting abilities. Tom Cavanagh has been fantastic this episode, slipping back into the old Wells yet being distinct than Earth-2 Harry.)
He proves Barry isn't who he says he is by using his super speed. Barry doesn't even flinch, so he admits he came back in time because he wants to go faster and Wells is the only person who has figured out how. But this piece of information tells Wells that he failed--that Eobard failed. (Uh-oh. I think this is exactly what they didn't want to do.) But Barry lies. He tells Wells he won--that he tricks him and while Barry travels to the past, Wells/Thawne travels back home to the future. Wells then says he doesn't need Barry, especially not this version. Barry threatens that if he dies, the real Barry of this time will learn all about Wells and how to defeat him, which means Wells--Eobard--doesn't go home. (Barry is so good, I can't tell if he's bluffing or not.)
Barry: Go on. Kill me, Thawne. See how this all ends.
Meanwhile, Cisco confronts Hartley about his special gauntlets. But then the Time-wraith shows up and chases Caitlin. (Oh no!) The three of them hide in Hartley's cell, hoping that will stop the wraith. But it doesn't; it starts cracking through the glass. They call for Barry, but they can't find him. Hartley reprograms his gauntlets to match the wraith's frequency, which scares it off. By the time Barry and Wells show up, the wraith is gone. However, this gets Cisco and Caitlin thinking, and they realize that Barry is the common denominator for the wraith's appearances. Wells tells Barry there is no way to stop a wraith; speedsters (yes, plural, as in there are more out there) just try to avoid them when they time travel.
Barry returns to his lab at the CCPD to look for clues. Barry talks to Eddie about Iris; he makes up an excuse for creating her a birthday video and he asks Eddie to record what Iris means to him. (I'm not crying, you're crying.) Cisco and Wells try to repair the gauntlets, but they can't do it without Hartley. But just then, past Barry shows up and asks where the "other Flash" is. Future Barry walks in. He explains to Cisco and Caitlin that he's from the future. (This is actually the best scene and round of dialogue.)
Cisco: "Wait a second, how do we know which one's the real Barry?"
Past Barry: "Dude, okay, I've watched Wrath of Khan with you like five times."
Future Barry: "Yeah, and every time at the end, you turn to me and say, 'I have been and always shall be your friend.'"
Cisco: "Haha! You impostor! What is going on here?"
They determine the only way to stop the wraith is for future Barry to return to the future. Wells takes Barry back into his super secret room (though, not handcuffed this time). He gives Barry a flash drive thing that supposedly has information on it about increasing his speed. Barry isn't completely happy with this compromise because he's worried Wells is playing him. But it's the only thing they have time for.
Future Barry prepares to leave in order to lure the Time-wraith away from Wells and the past. He tells Team Flash they have a year to figure out how to stop the wraith, and he tells Cisco that Hartley knows where Ronnie is. (Since that bit changed when he captured Hartley early.) Barry runs, letting the Time-wraith chase him, but it slows him down so he can't time-travel. Past Barry, despite Wells' protests, runs to his aid and boosts future Barry into the time vortex.
Barry arrives back in the future (or present, depending) where Caitlin and Cisco wait for him. Caitlin asks if he even traveled, but he doesn't answer. Instead, he warns them the Time-wraith is coming. Fortunately, Caitlin and Cisco did work on something to stop it within the past year. As it approaches to attack, Cisco pulls out a fancy gadget and blasts it. But it doesn't work. (Duh-duh-DUN!) The wraith gets past them and pins Barry to the ground. (Oh no!) It presses its nasty hand over Barry's chest and starts... sucking his life force? his speed force? out of him. (Ew.)
Then, Hartley, wearing his gauntlets, shoots a frequency blast at the wraith. It screams and vanishes. Hartley, then, comes over to Barry to welcome him back from his trip. Barry is surprised to see Hartley there and not... well... in the pipeline. (This is brilliant!)
Barry tells them about the trip. They go to the secret room and put the flash drive into the computer device. But it doesn't do anything. Frustrated, Barry pounds his fist on the device. A blue hologram flickers to life above them, showing numbers and equations. They have a way to increase Barry's speed!
Meanwhile, Harry is scrambling around. He hasn't been able to track Jessie, and he's frustrated. Barry reassures him, but Harry isn't optimistic. (Good pep talk, Barry!) Barry returns home to find Iris looking through pictures of her and Eddie. (Poor Iris.) She can't believe it's almost been a year since he died. Barry tells her she just needs to move forward. He shows her the video he recorded of Eddie. (I'm not crying, Iris is crying.)
Barry: Sometimes the only way to move forward is to revisit the things in your past that were holding you back. You have to deal with them head on, no matter how scary they may be. Because once we do, you'll see that you can go further than you ever imagined.
Barry returns to STAR Labs. He does another voice-over as he walks across the room and picks up Jay's helmet. Then he whispers,
"I'm coming for you."
What did you think of "Flash Back?"