The time travel episodes of The Flash are typically the show’s most narratively muddled, frustrating, and frankly dumb. It’s a remarkable relief that the series’ milestone 100th episode, directed by cast member Tom Cavanagh, somehow gets the time travel nonsense right and may be the best entry of the season.
Having identified Cicada, Sherloque and Ralph track his movements and determine that he visits his comatose niece in the hospital every night. Feeling cocky, Barry declares, “Let’s go get him.”
The problem, unfortunately, is how to do that. Cicada still has the dark matter dagger that can dampen the team’s superpowers. To get to him, first they need to destroy or eliminate the dagger. Nora suggests that they ought to build a more powerful weapon of their own that can negate the dagger’s powers. Doing so will entail going back in time to collect items from the team’s past adventures – specifically, a piece of Savitar’s suit and a “Speed Force transmitter” used by Zoom – and then infuse them with dark matter energy from the original S.T.A.R. Labs reactor meltdown. Once completed, Barry should perform a “time hack” by planting the weapon in the past at a place where it will be waiting for them in the present. (I’m pretty sure she got that idea from Bill & Ted.) Knowing what a mess he’s made of things when he’s time traveled previously, Barry insists on doing all this by himself, until Iris convinces him to take Nora along.
Sherloque is skeptical that Nora really came up with all these clever ideas on her own. He steals her journal and finds it filled with strange symbols that look very similar to the gibberish Barry wrote after he returned from the Speed Force prison last season. When he attempts to decode it, Cisco suggests that he should just ask Nora about it.
Back to Season 3
Barry and Nora race through the reactor core and open a time breach to the past, where Barry watches his prior self fight Savitar while he (the current version) and Nora hide in the background, a la Back to the Future Part II. What should be a simple plan to grab a shard of Savitar’s super-suit after it blows up gets complicated by the arrival of a Time Wraith, which doesn’t like speedsters mucking around with the timeline. Barry leads it away while Nora watches her mother shoot Savitar (a part of the story she didn’t know) and then grabs the shard.
Back to Season 2
Nora catches up with Barry and the two of them enter the Speed Force again. The Time Wraith chases them, but they dodge it and pop out in 2016, just in time to watch one of Barry’s confrontations with Zoom at S.T.A.R. Labs. After Barry and Nora find the transmitter device they came for, they’re spotted by Zoom, who chases them straight into another time tunnel. Just as he’s about to catch up with them, Zoom is grabbed by that pesky Time Wraith.
Back to Season 1
Barry and Nora tumble out of the Speed Force. Unfortunately, Barry drops and breaks the transmitter. Nora suggests that the only man smart enough to fix it may be Eobard Thawne. Barry is resistant to seeing Thawne again, but eventually sees no other option. He and Nora confront Thawne (in his disguise as Harrison Wells) in the Time Vault room at S.T.A.R. Labs.
Thawne quickly recognizes what’s happening, knows that this Barry is from the future, and identifies Nora as Barry’s daughter. He naturally has little interest in helping the two of them, but Barry convinces him that he’ll never get back to his own proper timeline unless he does. Thawne consents and repairs the transmitter for them.
Back to Day 1
Having acquired the two objects they need, Barry and Nora go further back to the night of the initial S.T.A.R. Labs meltdown. As Harrison Wells (really Eobard Thawne) prepares to initiate the reactor, he senses something wrong and nearly catches Barry and Nora spying on him.
Barry brings Nora to the Time Vault room. Nora asks why Barry hates Thawne so much, and he tells her that Thawne killed his mother. Apparently, the history lessons that Nora got from the Flash Museum were missing a lot of details.
Barry activates Gideon (voiced by Morena Baccarin again, at least it sounds like it), who isn’t in the slightest bit surprised to see him or Nora. She assists with redirecting dark matter energy into the Speed Force transmitter as soon as Wells/Thawne turns on the reactor and all hell breaks loose.
Before leaving this time period, Barry and Nora stop at the hospital and phase the weapon they’ve created into the middle of a support column, where it will await them in the future.
Back to the Present Day
Barry and Nora return to the very moment they left. To their friends, it feels like no time has passed at all.
With all the pieces of the plan in place, Barry suits up and goes to the hospital again, where he lures Cicada out to the parking lot. Cicada isn’t exactly pleased to see him. Vowing “Every meta-human must go,” the villain pulls out his dagger and prepares to strike. To his surprise, the dagger flies way off target and is pulled toward the Speed Force transmitter in the support column. Cisco immediately breaches it out, all the way to outer space.
Feeling triumphant, Barry puts a beat-down on Cicada. However, the victory is short-lived. Cicada’s attachment to the dagger is so strong that he’s able to recall it right back to him, even from Earth orbit. The dagger crashes to the ground and everyone else’s powers are nullified, until Caitlin transforms into Killer Frost and hits Cicada with an ice blast. She doesn’t seem affected by the dagger. Confused, Cicada flies away.
In the aftermath of this failed battle, Cisco can’t find any trace of either Cicada or the dagger. He and Sherloque theorize that Killer Frost is immune to the dagger’s powers because she didn’t originate from dark matter the way the rest of the meta-humans did.
Sherloque asks Nora about her journal, but doesn’t quite buy her story that the symbols are a special “time language” she invented to record the events of the timeline regardless of changes brought about by speedster time travel. After she leaves, Sherloque successfully decodes one passage from the journal as, “The timeline is malleable.”
Nora takes one more trip through time to spy on her grandparents on a peaceful night before Eobard Thawne will murder her grandmother. Barry follows her and they share a nice moment of bonding.
Later, however, Nora sneaks into the Time Vault and asks Gideon to scan a page from her journal. When Gideon asks where to send it, Nora decides to deliver the message herself. The next thing you know, she jets off to 2049 and meets another version of Wells, who may be an older Eobard Thawne. (It’s not confirmed.)
The episode then ends with an unrelated epilogue scene (the same one tacked onto the last episode of Supergirl) setting up next week’s Elseworlds crossover event.
I could quibble about a couple of things in this episode if I wanted to. For example, as the dagger flew back toward Cicada, why didn’t Cisco pop open a breach to, say, Earth-X, where Cicada wouldn’t be able to retrieve it? Maybe it all happened too fast for him to come up with that plan…
Otherwise, this is a pretty great episode that, despite all the time jumps and playing with past events, actually makes coherent sense and isn’t too confusing. As director, Cavanagh does a pretty skillful job of sprinkling in fan-service for the 100th episode and integrating clips from old episodes in a way that feels fresh. The story works and the emotional beats hit. This is The Flash firing on all cylinders. I wish they were all this good.