The Flash returns with its season 1 finale episode on 19 May at 8pm on The CW.

Episode 23 is titled Fast Enough, where Barry will travel back in time to save his mother.

Click here to watch the episode online on The CW's website.

Fast Enough will pick up from where Barry keeps the Reverse-Flash prisoner after having him captured in the last episode. The finale will find Barry in a big dilemma about whether or not he should travel back in time to save his mother's life.

But there could be huge consequences if he does save his mother. For one, he might never meet anyone in STAR Labs, and two, he might never become the speedster in the first place.

According to rumours, Barry saving his mother might create an alternative timeline called the Flashpoint Paradox, like in the Comics.

In the comic book event Flashpoint, Barry Allen travels back in time to save his mother and the results are disastrous. The timeline is so disrupted by the change that the world becomes almost apocalyptic and terrible. Heroes become villains and lifelong friends are at war.

A new promo for the finale also teases an apocalyptic-type-event.

"I dreamed my whole life about saving her," says Barry in the promo video. "This is why you became the Flash" Joe tells Barry, adding, "There is no choice here, Barry. You have to do this, you have to change the past."

But the one-minute video shows the whole world falling apart, because of the warped timeline as Cisco shouts, "He is being erased from existence."

The last scenes show Barry at the night of his mother's murder, and Nora Ellen asking, "Who are you?"

"It's me, mum, Barry," says The Flash with tears in his eyes.

What is Eobard Thawne's endgame?

Viewers know that Eobard/Harrison Wells wants to get home. But why did he travel back in time in the first place? Tom Cavanagh, who plays the time travel bandit, promised that all will be revealed in the finale.

He told The Hollywood Reporter, "We're not looking to shortchange people." In a preview clip, Thawne reveals he will be born 136 years from now — and has a monologue on why he killed Barry's mother.

Here is the official synopsis of the episode.

Wells (Tom Cavanagh) presents Barry (Grant Gustin) with a life-changing choice. Dr. Martin Stein (guest star Victor Garber) and Ronnie Raymond (guest star Robbie Amell) return to help the S.T.A.R. Labs team with this final fight.