The future has played a significant role on The Flash from the very beginning and season 3 is no different. Savitar, this season's main antagonist, is more than acquainted with Barry in the future -- it's his imprisonment in the Speed Force by future-Flash that is the very reason he's here in the present. The threat that Savitar now poses to Barry is his killing of Iris in the future -- something which all evidence still points to as happening, meaning that nothing Team Flash has accomplished this season has changed that future.

Tonight, The Flash season 3 returns from a short hiatus with 'The Once And Future Flash' -- a debut directorial for Tom Cavanagh from a script by Carina Adly MacKenzie -- which sees Barry finally face what's coming head-on, deciding once and for all to visit the future and find his own answers. Seeking those answers will have Barry encountering future versions of himself and friends who have been deeply affected by Iris' death, painting a very bleak outlook for Team Flash if Savitar cannot be defeated in time. But Barry, ever the optimist, won't give up until he gets what he came for -- Savitar's true identity. Will the future share that answer with him?

"I'll Never Tell..."

Killer Frost Season 3 The Once And Future Flash

It was during the final moments of 'Abra Kadabra' that Caitlin transforms into Killer Frost, unleashing her ice powers (and even icier personality) on her friends. 'The Once And Future Flash' picks up with these events still in progress, as Frost toys with Julian, Cisco, and H.R. before The Flash arrives and sends her running. She escapes, and as is revealed to Barry by future-Cisco later on in the episode, it is the last time she ever sets foot within S.T.A.R. Labs.

A return from Killer Frost was one of the ominous headlines leading up to Iris' death, marking this as just another instance in where Team Flash fails to change the outcome. If time truly is like a river, then its current is stronger than ever, forcing these events to occur no matter what. And if being unable to save Iris is Barry's greatest failure, then allowing his friend to become a twisted and evil villain is a close second. In this case, it's also revealed Killer Frost will have a much larger role to play in Savitar's plans than anyone would have guessed, making Caitlin's descent into villainy all the more tragic.

Not only does Killer Frost fully consume Caitlin, she almost immediately teams up with Savitar. She then, either before or after Savitar kills Iris (an act Frost is almost certainly an accessory to), duels with Vibe in a battle that's been teased several times already this season. Only in this episode, we learn how it ends -- with Killer Frost freezing off Vibe's hands! After maiming her former best friend, Frost is eventually apprehended and imprisoned in a special cell in Iron Heights with Julian as her jailer. She is remorseless and cruel (a change of character Danielle Panabaker clearly relishes getting to play), and when past-Barry visits she refuses to reveal to him Savitar's identity, coyly whispering "I'll never tell..."

It's interesting to learn Killer Frost chooses to join Savitar, in part, because he isn't trying to change her. Instead of a cure, he offers her acceptance -- something her friends never even tried. Of course, Savitar's acceptance doesn't discourage her from becoming an evil villain, and as it stands, he's the first to reach her -- revealing to her his true identity and easily winning Frost to his side.

Learning to Live With the Unimaginable

Barry Allen Season 3 The Once And Future Flash

Barry's trip to future finds him again wrestling with the idea that all he's ever done is make life worse for those closest to him -- including himself. After Iris' death, Barry becomes a shell of the man he once was, abandoning his friends and family to wallow in his own pain. Wally flies off in a rage and fights Savitar himself, only to be found later with a broken spine and in a catatonic state. With his children either dead, unresponsive, or missing, Joe is consumed with grief. Cisco, no longer able to vibe since losing his hands, hangs around, listless, hoping that one day things will return to the way they were. And Julian, clearly guilty over his role in initiating Caitlin's downward spiral, serves as her jailer, constantly reminded of what might have been. The only member of Team Flash who is doing all right is H.R. -- just as Savitar predicted.

However, unlike previous times that Barry learns he's made life terrible for everyone, this time he might be able to do some good. Barry hoped he'd learn the secret to beating Savitar (and he may have if he can track down Dr. Tracy Brand), but what the future actually showed him is that he can't turn his back on his friends -- especially when things are at their most bleak. Being unable to save Iris makes for an awful future, but it's only made worse when Barry pushes everyone away.

Whether or not Barry saves Iris is the very moment on which season 3 teeters, but in 'The Once And Future Flash', Barry is a shown a future in where he fails. And instead of simply giving up on that future, he chooses to remain and instill some hope in that future. Those are the actions of hero, and for Barry's sake, let's hope he can muster that same attitude when and if the unimaginable actually happens.

Just Who Is Savitar?

Savitar Kills Iris West

Along with whether or not Iris dies, the other major question plaguing The Flash season 3 is who is Savitar? Obviously, the series was going to remain tight-lipped on this one as long as it could, but it seems next week Savitar's is finally unmasked. That makes this week the last chance to weigh in with your guesses, so let's look at the new evidence from 'The Once And Future Flash'.

Killer Frost learns Savitar's true identity right at the very end of the episode, with her future self confirming this earlier on. She is stunned when she sees who's actually inside Savitar's suit, leading us to believe it must be someone important to her. But we also learn of Wally's reaction to learning Savitar's identity, and it presumably shocks him so severely that he can't even speak. This implies it must be someone of significance to both Caitlin and Wally. And there's only one person whose sudden reveal as The Flash's greatest adversary who could have that kind of impact on both of them.

Next: The Flash Season 3 Finale Synopsis Promises a Cliffhanger

The Flash season 3 continues next Tuesday with 'I Know Who You Are' @8pm on The CW.