The Flash Is Heading To "Supergirl," But How Will "Supergirl" Tie Into "The Flash"?

On March 28, worlds will collide when The CW's Flash -- Grant Gustin -- shows up from an alternate universe to team with CBS' Supergirl, Melissa Benoist. This isn't the first time the shows have crossed over, either; on the February 9 episode of "The Flash," Barry Allen glimpsed Supergirl as he ran through a breach between his universe (Earth-1) and the parallel universe of Earth-2.

RELATED: Gustin Teases Next Flash/Supergirl Crossover May Include "Arrow," "Legends of Tomorrow"

So we know Barry will probably run through another breach, and somehow end up on "Supergirl." But the big question no one seems to be asking is, how will this tie back in to "The Flash?" If, that is, it does at all?

Viewers will find out how it all works soon enough, but in the meantime, we can speculate wildly on just how connected the crossover will be. The way I see it, there are three distinct possibilities.

SCENARIO #1: The Flash Is About To Get Lost In Space

If you're not totally caught up on "The Flash" (and you should be, it's excellent), you should know there's a big problem with Barry just casually jogging over to an alternate universe. At the end of February 16's "Escape From Earth-2," Team Flash managed to close every breach between their universe (there were 52, of course) and Earth-2 in order to trap the villainous Zoom.

But when Zoom appeared to kill their friend and ally Jay Garrick (Teddy Sears) in the process, they spent most of the next episode trying to figure out if they could -- and should -- reopen the breach to Earth-2 in order to rescue Jay and defeat Zoom.

Let's be real: of course they're going to figure out how to do that. "The Flash" team isn't going to spend the rest of the season saying, "Well, too bad we couldn't wrap up that Zoom mystery! Byeeee." And at the pace the show moves, it's going to happen sooner, rather than later.

For my money? It'll happen by the end of March 22's episode, "Trajectory." If the breach gets reopened, and Barry doesn't keep his eyes on the prize -- when he first ran through the breach, Jay warned Barry to not get distracted, because he could get lost in the multiverse -- he'll end up somewhere other than Earth-2.

Whether the end of the March 22 episode explicitly sets up the March 28 crossover is certainly up for debate, but I'd bet the "Supergirl" episode will mostly stand on its own. Barry will explain he got lost, and by episode's end he'll be back on track for the beginning of the March 29 episode of "The Flash."

Maybe he'll reference the crossover later to Cisco, or maybe it'll get swept under the rug. But it makes sense for the CBS episode to fit neatly in between episodes of "The Flash." Basically, what we surmise about The CW show from this scenario is that Team Flash will re-open the breach -- and in fact, it's about to happen next week -- which is a pretty big deal. The last time the breaches opened, a giant black hole almost sucked in all of Central City. So, fingers crossed everyone makes it through this one a-okay.

SCENARIO #2: Crisis On Infinite Earths

This scenario dives even more deeply into speculation, but Season 1 of "The Flash" dealt with time travel, and Season 2 opened up the possibility of alternate worlds. They're definitely not going to make Season 3 a small, insular story about Barry and his friends exploring how to run a successful coffee shop over at CC Jitters.

Instead of the "Supergirl" episode taking place between episodes of this season of "The Flash," what if ittakes place after this season? After all, ending Season 2 with not only the breach between Earth-1 and Earth-2 open, but an entire multiverse there to explore would fit the bill as a massive moment and major cliffhanger.

And while we're wildly speculating, the very first episode of "The Flash" teased that in the future, the her would be lost in a "Crisis." Barry has already changed the course of time over these first two seasons, so what if that "Crisis" event happens even sooner? What if Season 2 ends with Barry lost in time and, in a turn of events that would make DC Comics' fans heads explode, he ends up having to unite all the DC superhero shows to battle some ultimate evil next season?


Okay, calm again. The advantage of this scenario is that it wouldn't depend as heavily on the watching order of the episodes. Whatever status quo "The Flash" is left in at the end of Season 2, this upcoming episode of "Supergirl" could take place in that indeterminate future, teasing upcoming events on "The Flash" without spoiling them.

Though I think the "Crisis" scenario is a long-shot, it would be consistent with how DC TV has seeded Easter eggs for events, sometimes far in the future. Plus, it dovetails nicely with Gustin's comments last week teasing a crossover between the current crop of DC Comics-based television shows.

SCENARIO #3: It's Totally Unconnected

Honestly, given how much care the DC/Warner Bros. team puts into their superhero shows, teasing out Easter eggs and making sure everything remains as consistent as possible, I don't think we'd see Barry Allen show up on CBS's "Supergirl" only to never have it referenced in any way on "The Flash." But it's possible!

Hey, he could be an alternate universe Barry. Or, given that not everyone who watches "Supergirl" watches "The Flash" and vice versa, it could just be a fun lark. Superhero fans can accept a lot, so just having Flash mention, "Yeah, I can run through universes and I got lost," might be enough.

It's not, though. Enough, I mean. But it is a possibility!

Whatever happens, we'll know more when the crossover arrives on March 28. Now let's get Green Arrow (Stephen Amell) on "Gotham" -- he'd take care of Hugo Strange and company in no time.

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