"The Flash" returns Tuesday for the CW series' second season and things will pretty much pick up right where the show left off for Barry Allen (Grant Gustin) and the S.T.A.R. Labs team. However, fans might need a little help remembering how exactly Season 1 ended after a confusing, time-travel filled showdown with Dr. Wells (Tom Cavanaugh) in the finale.

Episode 23, "Fast Enough," began with Barry interrogating Dr. Wells, or should we say Eobard Thawne. Thawne confessed to Barry why he had killed his mother. In the future the Flash and Reverse Flash are hated rivals, endlessly pitted against each other with neither strong enough ever to destroy the other. Thawne learned the Flash’s identity and traveled back in time to kill Barry as a boy. Barry, though, followed him and rescued his younger self, but Thawne killed Barry’s mother in retaliation.

Thawne made his protégé an offer. If Barry would use his speed to open a wormhole to let Thawne return home, Thawne would give Barry a chance to go back and save his mother. However, altering that night would rewrite history. Barry would never live with Joe (Jesse Martin) and Iris (Candice Patton) and, likely, never become Flash and meet Cisco (Carlos Valdes) and Caitlin (Danielle Panabaker).

To Barry’s surprise, Joe suggested Barry take the deal. He wanted him to have the chance to grow up with his real parents. Barry was even more shocked, though, when his actual father (John Wesley Shipp) told him not to do it. Henry Allen said he was so proud of the man Barry had become and would not want to risk him turning out differently, even for his freedom and his wife’s life.

A torn Barry talked to Iris, who advised him to do, for once, whatever he wanted to do and stop thinking about other people. For Barry, that meant going back into the past. To do so, according to Thawne, they would have to turn on the particle accelerator, with Barry taking the place of one of the colliding particles. If he went fast enough, he would create a wormhole allowing Thawne to return home and Barry to get to his mother. If he was too slow, though, he would die.

Cisco was tasked with building a vessel that would allow Thawne to traverse the wormhole despite his inhibited speed. Unfortunately, when he came across a heat problem, he had to consult Thawne himself. During the conversation, Cisco confronted his former boss about the alternate reality in which Thawne killed him. Thawne was shocked. If Cisco could remember the parallel reality, then it meant he had been affected by the particle acceleration.

On top of that, Dr. Stein (Victor Garber) realized there was another problem. Thawne’s plan had the possibility of creating a black hole that could destroy Central City and, potentially, the whole world. For Thawne, that was a minor risk, but Barry had a lot to ponder, especially since he was leaving so much behind. In a very emotional moment, Barry admitted to Joe how hard it would be to leave a person he considered a father behind. Plus, with Barry considering leaving, Eddie (Rick Cosnett) had gotten his mojo back and patched up things with Iris.

Thawne’s plan worked and when Barry reached Mach 2 speed, he was able to run back in time to the night his mother was killed. However, once there, he did not try to save his mother, instead letting Reverse Flash stab her once again while he watched in tears. He did comfort his dying mother (Michelle Harrison) after Reverse Flash left, revealing his identity to her and getting the chance to say a heartfelt and tragic goodbye. Eventually, though, he had to race back to the present before the wormhole closed, having chosen to keep his current life.

When he got back, he stopped Thawne just before the villain was about to take off into the wormhole. The two fought an epic battle, but Thawne gained the upper hand. However, just before he was about to kill Barry, something happened. Eddie, who had listened to a speech from Dr. Martin earlier about coincidences, realized he was not a coincidence in this story. As Thawne’s ancestor, if he died, Thawne never would be born. Eddie shot himself, erasing Thawne from existence and dying in Iris’ arms a hero.

Unfortunately, their problems were still not over; the wormhole collapsing on itself was causing a black hole that was threatening to swallow Central City. As the finale went to credits, Barry rushed off on an impossible mission to save the city and the world.

So, what will happen now? Fans will have to watch to find out. "The Flash" Season 2 premiere airs Tuesday at 8 p.m. EDT on the CW. 

Watch the Season 2 trailer below: