May 19, 2015 10:10 AM

Barry Allen’s whole life has been shaped by witnessing his mother’s murder as a child, and his father’s subsequent prison sentence after he was wrongly accused of the crime.

In The Flash‘s dramatic finale, Barry (Grant Gustin) is presented with the opportunity to go back in time 15 years to save his mother, but at “unparalleled risk,” as Dr. Stein (Victor Garber) explains in an exclusive sneak peek.

With Ronnie (Robbie Amell) by her side, Caitlin (Danielle Panabaker) is all for the idea – “The chance to be with someone you love seems pretty cut-and-dried to me.”

However, though nobody involved would even remember the difference, Cisco (Carlos Valdes) is upset by the idea that he and Barry may never meet in the parallel universe that would be created by this decision.

It seems an easy choice for Barry to go back and save his mother and keep his father from prison, but he knows it means he’d never end up living with Joe (Jesse L. Martin) and Iris (Candice Patton).

“Truth is, there’s no real way of knowing what your life will be,” Dr. Stein tells Barry.

The Flash Cast Teases the Finale

In the current timeline, Dr. Wells/Eobard Thawne (Tom Cavanagh) previously revealed that Barry and Iris end up marrying – but Gustin told PEOPLE at the CW upfronts on Thursday that Barry is not really factoring Iris into his life-changing decision. “As Barry has said – and which I truly think he believes – is that he wants her to be happy and he wants Joe to be happy. If, ultimately, they wouldn’t know the difference if Barry changed the past, he’s not really worried about his relationship with Iris at this point.”

Added Gustin, “It’s more about his family and making sure everyone’s going to be okay. He feels that this is the best, safest decision to make for everybody.”

Speaking of Iris, Patton told PEOPLE that her relationship with Eddie (Rick Cosnett) is “still evolving” despite the fact that he broke things off in “Rogue Air” after Eobard told him about Iris and Barry’s future. “[Their relationship] is not quite over.”

Meanwhile, Valdes promised PEOPLE that a “huge reveal” is coming in the finale and a “big confirmation of certain questions … [Cisco] comes to knowledge about some information that changes his trajectory.”

Finally, now that we know Wells is not actually Wells, what’s going to happen to S.T.A.R. Labs? Many have theorized that it’s up to Cisco – who has shown increased maturity throughout the season – to assume the mantle. However, as Valdes told PEOPLE, “It’s such a difficult space to film in, at times, that I hope they blow it up!”

The finale of The Flash airs Tuesday (8 p.m. ET) on The CW.

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