On The Flash's Tuesday finale, Barry (Grant Gustin) travels back in time to try and save his mother's life, and thus also save his father from a life in prison. That seems like a fairly noble mission, until you take into account all the repercussions traveling that far back in time could have on the world.

Gustin admits Barry's trip to the past "doesn't necessarily go as planned," and that everything we knew about his future — including his future marriage to Iris (Candice Patton) — is now up in the air. But that might not be the biggest news. "What's fun about this show is that there's going to be multiple timelines as we move forward," Gustin says. "I think we're going to start showing Earth-One and Earth-Two in the near future. There will be kind of different dimensions going on."

Why we need the Arrow-Flash spin-off

In DC Comics, Earth-One and Earth-Two are only a few of the parallel universes that make up the elaborate multiverse. Having an Earth-One and Earth-Two within The Flash would open up radical new possibilities for the show, including alternate versions of characters we already know or even new versions of the same superheroes, such as Jay Garrick's The Flash or perhaps the superhero or villain sides of Cisco Ramon (Carlos Valdes) and Caitlin Snow (Danielle Panabaker).

However, having parallel universes could make the future cross-overs with Arrow and Legends of Tomorrow that much trickier. "It gets a little Rubik's Cube-y in terms of keeping consistency between all these timelines and whatnot," Valdes says. "But the writers have their stuff together. If I were to trust anyone, it would be them."

The Flash's first season finale airs Tuesday at 8/7c on The CW.

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