Warning: SPOILERS for The Flash season 6 finale.
The Flash season 6 finale, "Success Is Assured", was notable in several respects, ending with most of the seasons' subplots left unresolved and an unprecedented number of cliffhangers. It was also the first time in the series' history that the season's main villain accomplished their ultimate goal and was established as returning next season.
It seems likely that this was entirely due to the shooting delays caused by the coronavirus outbreak. The season finales for nearly all of the Arrowverse shows were bumped up and re-edited after it became clear that they would not be able to finish filming the original finales in time for the May Sweeps period. In the case of The Flash, production stopped with 20 of the season's 22 episodes completely filmed.
Originally, The Flash season 6 was meant to end with the return of the Reverse-Flash and a big cliffhanger heading into season 7. Despite this, the season still comes to a suitable conclusion, with several small cliffhangers and the biggest metahuman battle in the show's history.
Mirror Mistress' Plan In The Flash Season 6 Finale
The second half of The Flash season 6 focused on the efforts of Dr. Eva McCulloch aka Mirror Mistress to escape from the mirror universe she'd been trapped in for six years. and avenge herself by killing her husband, Joseph Carver. Dr. McCulloch claimed that Carver took advantage of her being sent into another dimension by STAR Labs' particle accelerator explosion to take over her company and establish himself as the leader of the criminal cabal known as Black Hole. Carver, in turn, claimed that he had tried to rescue his wife, but the experts he employed told him that the Mirrorverse distorts people like a fun-house mirror and that the woman who claimed to be his wife was just a twisted copy who thought she was Dr. Eva McCulloch.
It was unclear who was telling the truth, but Barry Allen was unwilling to stand by and let Dr. McCulloch kill her treacherous husband, even after Carver confessed that he had allowed Iris West-Allen to be drawn into the Mirrorverse and kept her whereabouts a secret. Barry also refused to negotiate with Mirror Mistress after she offered to release the real Iris in exchange for him looking the other way as she killed Carver. This set up an epic battle within McCulloch Technologies, as Team Flash faced off against the newly dubbed Mirror Mistress and her allies. These included Sunshine, Dr. Light, and Ultraviolet; three light-themed metahuman assassins whom Carver had forced into his service and whom Mirror Mistress promised to free if they helped her get to her husband. In the end, Mirror Mistress' success was assured. She stabbed Carver to death with the shards of the mirror that once imprisoned her as a helpless Flash watched.
Later, Mirror Mistress held a press conference where she claimed to have been held hostage by a criminal organization for six years and to have been reunited with her husband just before his violent death; a technically true statement, though she left several fine details out of her story. Curiously, despite having the ear of the world, Eva made no effort to out her husband for his crimes as the leader of Black Hole or ruin his reputation. At first, Eva was singularly motivated in her revenge plot, but when she realized what her husband was up to in the real world, her plans transformed and now she's looking forward to become an even bigger villain than she already is. This implies that Mirror Mistress will be making use of Black Hole's resources herself in The Flash season 7, now that she has accomplished all of her other goals. Given that she was the real brains behind McCulloch Technologies, this could make Black Hole and its operatives more dangerous than ever. That, coupled with the suggestion that she may be a warped mimic of the real Eva McCulloch, makes her far more menacing than she was throughout season 6.
Sue Dearbon Twist Explained
One of The Flash season 6's most endearing subplots involved Ralph Dibny and his search for missing debutante Sue Dearbon. The Elongated Man finally caught up with her in "A Girl Named Sue," and discovered there was more to her than met the eye. Far from a spoiled party girl, Sue was an accomplished thief who played Ralph for a sucker and used him to help her rob a bank. The reason behind her criminal acts was because she was being blackmailed by Joseph Carver. In order to combat this, Flash and Elongated Man infiltrated one of Black Hole's bases, which was ultimately burned to the ground by Mirror Mistress' minions. The silver lining there was that Sue and the Dearbon family could no longer be blackmailed since Carver's files were all destroyed.
However, later in The Flash season 6 finale, it was revealed that the real reason Carver wasn't blackmailing Sue anymore was because she had agreed to become a Black Hole agent in exchange for her parents' freedom, while secretly planning to use her new position to get close to Carver and kill him. Just like Eva, Sue also had a revenge plot in mind, one that had a higher chance of being successful considering she was already on the inside with Black Hole, whereas Carver was actively avoiding his wife. While Ralph ultimately persuaded Sue to abandon her plan to kill Carver, it was too late as she had inadvertently put herself in the position to be framed by Mirror Mistress instead for Carver's murder.
The Flash season 6 finale ended with Sue Dearbon as the most wanted fugitive in Central City. It's never revealed why Mirror Mistress chose Sue as the scapegoat for Carver's death or how she did it either, but it is clear there was enough evidence piled up against Sue to make her a convincing patsy. With her history with Carver and the fact that she had a convincing motive to kill him, whereas Eva didn't (at least to the public, that is), Central City PD wouldn't have a problem believing Sue really did kill Carver. That's the in-universe reason; the behind-the-scenes decision to frame Sue may have been motivated by the fact that the writers needed a reason to keep her around without prolonging on her side story. Sue Dearbon marries Ralph Dibny in the comics, so this twist ending was merely a device to push that relationship forward in The Flash season 7.
Can Caitlin's Mother Heal Frost?
Dr. Caitlin Snow and Frost were largely absent from the action of The Flash season 6, due to actress Danielle Panabaker's pregnancy. The sudden disappearance of the frosty hero and STAR Labs' resident biologist was explained away as complications caused by Frost (who dropped the "Killer" label from her name early on in season 6) being shot by Dr. Light. With Frost's ice-healing powers on the fritz and Caitlin lapsing into a state of hibernation in "Pay The Piper," it was decided that Team Flash needed to bring in a specialist who might be able to help Caitlin and Frost to stabilize their body. One quick scene in the Flash season 6 finale revealed that Frost and Caitlin's mother, Dr. Carla Tannhauser, was taking them to a Tannhauser Industries facility in the Arctic Circle where they could recover in private.
Given the circumstances of the storyline, there's no reason to believe they won't return in The Flash season 7 and the biggest question is if Caitlin's mother can truly heal Frost. Taking into account Dr. Tannhauser's past, it would seem likely that she could work something out for Frost. After all, she and Julian Albert were able to concoct a temporary cure for Killer Frost's powers in The Flash season 3, so she could build off what she discovered before while simultaneously concluding a dropped plot thread.
Why Flash Is Still Losing His Speed
It was revealed in "The Death of the Speed Force" that Barry Allen introducing Spectre's powers into the Speed Force during Crisis on Infinite Earths led to the source of his power being corrupted and ultimately destroyed. This left Barry with only the residual Speed Force energy within his body to depend upon, and his powers began to wane and become more erratic as a result. Team Flash attempted to solve the problem by following in the footsteps of the Reverse-Flash and create their own artificial Speed Force.
This point was briefly touched upon in The Flash season 6 finale, with Barry having a conversation with Caitlin about how his velocity was still decreasing and it was getting worse because he was so stressed out over Iris being trapped in the Mirrorverse. His distress wasn't helped by Joseph Carver's contention that anyone who was drawn into the Mirrorverse would eventually be driven completely insane. The continued difficulties in constructing an artificial Speed Force to rescue their allies were also used to explain the absence of Cisco Ramon, who had traveled to Atlantis one episode earlier to secure the final piece of equipment he needed for his plan to breach the Mirror Universe and rescue everyone being held hostage there. It seems likely that the perpetual motion engine Cisco spoke of will also play a role in creating the artificial Speed Force, being a source of infinite power than can presumably find a way to power Barry's body.
What Happened To Iris In The Mirrorverse
The final scene of The Flash season 6 finale focused on Iris West-Allen and Kamilla Hwang, who had begun trying to use the equipment at STAR Labs' building in the Mirrorverse to find a way to escape on their own. Unfortunately, Iris became increasingly agitated the more she tried to look at the various computer screens and focus on what they said, exhibiting nervous twitches identical to those suffered by Mirror Mistress when she was in the Mirrorverse. Shortly after Iris successfully used STAR Labs' satellite to locate the real Chief Singh in the Mirrorverse, she suddenly keeled over and began to glow. Her skin crystallized and she vanished without explanation, leaving a confused and terrified Kamilla behind.
The special effects used to show Iris' body crystallizing were similar but distinct from the ones exhibited by transformed objects shot with McCulloch Technologies' mirror gun, suggesting Iris was teleported somewhere rather than fading out of existence. The obvious implication is that the Mirrorverse has begun to change Iris, but is she gaining powers akin to those of Mirror Mistress? Or was this another force acting upon her? The reason that all this happened Iris and not Kamilla, at least right now, is because she had been in there longer. What's more, she was making the more dangerous attempt between her and Kamilla to try and escape the Mirroverse.
Is Barry Still Barry?
One question which is raised by Nash Wells but seemingly forgotten about halfway through The Flash season 6 finale concerns Barry Allen's state of mind, and the possibility that someone is controlling his actions. Perhaps it is no coincidence that Barry was accused of being one of Mirror Mistress' mirror duplicates two episodes earlier in "Liberation." In any case, the many versions of Harrison Wells who share a brain with Nash told him that there was no way Barry Allen would ever bargain with a villain and sacrifice someone else to save his wife's life, and yet, Barry allowed a mirror duplicate of Captain Singh to get close to Carver and listened to him as he offered to exchange Iris' freedom for Carver's life.
While Barry defended his actions as something any husband would do when his wife was in danger, it still raised the troubling possibility that Flash is not entirely in control of himself as The Flash season 6 comes to an end. No matter what odds have faced him, Barry Allen has always had a moral center that he rarely - if ever - wavers from, so him considering sacrificing someone, even a villain, can constitute as evidence that he's been replaced. Still, Barry's bargaining with villains is not entirely unheard of and he's never thought logically when Iris is concerned. It's certainly possible that Barry may have considered making some sort of deal with Mirror Mistress since she's the lesser of the two evils between her and Carver. If Barry has truly been replaced, this might have been revealed in the lead-up to the original Flash season 6 finale, but due to production delays, this may instead be an early season 7 twist. Or it could be abandoned altogether in order to quickly move past The Flash season 6's story when season 7 starts.