The Flash‘s potential — as vast as its hero’s array of abilities — was established back in its pilot episode; and that potential has steadily increased with each new challenge Barry Allen has faced throughout this season. But “Out of Time” is a watershed moment for the rookie CW series, in that it introduces the most valuable ability any superhero or TV show can possess: the power to obliterate expectations.

The idea that Barry might be able to travel through time has been addressed before, but until we actually see it incorporated into the show’s storyline — as we finally do here — it’s difficult to comprehend its weight. So when Barry does puncture the time barrier in this week’s episode, it’s both poetic and meta. So much happens (particularly in the third act) that Barry’s climactic realization of what he’s done hits him at the same time we learn everything we’ve just witnessed may or may not necessarily have happened.

But first a step back… “Out of Time” begins with the events of the first episode, when Joe West chased criminals Clyde and Mark Mardon straight into the explosion of the particle accelerator, which resulted in Clyde becoming the first Weather Wizard, who was killed fighting Joe and the Flash. Mark, we now learn, acquired the same powers as his brother, but he has greater — almost pinpoint-accurate — control over them, and is out for revenge from West.

Fortunately, Cisco was working on a “wizard’s wand” (which looks a little like a cross between a Dalek ray gun and a sonic screwdriver) at the time of Clyde’s death, in order to take away the “natural electrical circuit” his powers tapped into. Barry confronts Mark with the device, but not before he aims a deadly bolt at Joe, which is intercepted by Captain Singh, landing him in the hospital with partial paralysis. Joe’s determined to stop Mardon, but gets taken hostage. Bloody and broken, he’s held captive on the waterfront and forced to watch as Mardon creates a tsunami to wipe out Central City and kill his daughter. The Flash intervenes, of course, or at least tries to. But he runs so fast he winds up going back in time to the beginning of the episode.

What gives the cliffhanger ending such import is that shortly beforehand Barry learns Iris has feelings for him, and they share a lingering first kiss before he’s forced to reveal his identity to her in order to save the city. Granted it’s debatable whether or not Barry could simply run away from Iris before she realizes what’s happening. But it does the job of giving Barry everything he’s wanted — allowing him to win Iris’ love and finally share his secret with her — before pulling the rug out from under him in the final scene.

Cisco, meanwhile, has a somewhat less pleasant realization than Iris, when he tests the containment field in which he believed he’d trapped the Reverse-Flash, only to find it never actually held the evil speedster. Wells finally comes clean and tells Cisco — in a highly disturbing scene, since we know how powerful he is — that his real name is Eobard Thawne, that he’s from the future, and that’s he’s been marooned in this time period; hoping for a way back via the Flash, who he once tried to kill but wound up murdering Barry’s mother instead. He also tells Cisco that the young scientist has shown him what it’s like to have a son — and kills him with a super-speed hand to his heart…

Given that Cisco appears in the trailer for next week’s episode, we know he’s not really dead, or at least he won’t be for long. But how many of this episode’s other events will prove immutable? All of Central City is in peril, Caitlin has learned Wells can walk, Iris knows Barry’s the Flash, Barry knows Iris is in love with him, and so does Eddie. If even one of these remains true, the course of the series is forever altered.

Accelerated Particles

— I want to feel bad for Linda when she discovers Iris has feelings for Barry, but I just don’t know her well enough. Here’s hoping that we’ll at least learn a little about Ms. Park’s background before she walks away.

— Cisco likes Buster Keaton movies? Is there no end to this nerd’s good taste?!

— Joe West is not only relaxed when he’s targeted by a revenge-driven metahuman, but he’s totally fine with hearing Barry describe his feelings for his daughter. Chillest guy EVER.

— “Excuse me, I’m gonna go stretch my legs.” The sly double meaning of Wells’ remarks just never gets old.

— Mark admits to West that Clyde was no saint, thus implying he was the nicer of the two brothers. Even more so than his superior powers, it’s a beat that makes Mark more interesting, since we now know he didn’t begin as a homicidal maniac.

— After temporarily losing his powers, how does Mark run out of a police station full of cops — whose Captain he’s just maimed — without getting apprehended by at least one of them?

— “Alright, fine, I will watch every episode of The Walking Dead with you.” That’s quite a commitment for a non-fan. Could love one day be in the air for Caitlin and Cisco? They’re hella more interesting than Caitlin and Ronnie.

— Nice to know that the Captain is gay and engaged. Kudos to The Flash for continuing to showcase diversity in its characters.

— For someone who’s always mucking about with rain, wind, and other elements of nature, Mark is incredibly well groomed.

— Cisco’s admission that he’s not all that close with his family makes his betrayal by Wells that much more painful.

— “Forgive me. But to me you’ve been dead for centuries.”

Next week: Captain Cold returns and Barry learns his rupture of the time barrier may have serious consequences.

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What did you think of this week’s episode? Let me know in the comments below or on Twitter (@JMaCabre).