Plot

Barry Allen uses his super speed to change the past, but his attempt to save his family creates a world without super heroes, forcing him to race for his life in order to save the future.

Barry Allen is struck by a bolt of lightning and thus, an extraordinary power is born inside him: The Speed Force. When he uses this power to run back in time and save his mother, he creates a world without heroes and General Zod has returned. To defeat him, his only hope rests in the hands of a retired Batman, another Barry and an imprisoned kryptonian.

Worlds collide when Barry uses his superpowers to travel back in time in order to change the events of the past. But when his attempt to save his family inadvertently alters the future, Barry becomes trapped in a reality in which General Zod has returned, threatening annihilation, and there are no Super Heroes to turn to.—Nikki D

Barry Allen has always been well-known as The Flash as he continues to juggle between civilian life and his superhero duties. However, in an attempt to save his mother from being killed, Barry travels back in time using his powers. However, whilst going back to his own universe, he is horrified to discover that he has created a timeline where superheroes are almost non-existent; this is made even worse when an alternate General Zod returns to try and destroy the world. Now with the help of an alternate and elderly Batman, an unfamiliar Kryptonian, and even his younger self from the past, Barry must stop Zod's evil plan and hopefully travel back through the space-time continuum in order to restore his universe back to the way it was.—Affan Jamsari

Barry/The Flash helps Bruce Wayne / Batman (Ben Affleck) and Diana Prince / Wonder Woman (Gal Gadot) stop a robbery in Gotham City. The robbery was led by Falcon's kid who decided to break into the lab at Gotham General Hospital to steal a highly deadly virus and then blasted his way out with a crew. Batman gives pursuit. The Flash is tasked with saving people at the hospital which is starting to crumble due to a large sinkhole left by the robbers. As the East Wing of the hospital collapses, The Flash rescues several newborn babies' mid-air from falling to their deaths. Batman manages to stop the robbers over a bridge by the vials of virus are about to drop into the river, which would wipe out half of Gotham city within a few hours. Wonder Woman arrives at the last minute to rescue the vials safely. The Justic League are coordinated by Bruce's butler Alfred Pennyworth (Jeremy Irons).

Barry (Ezra Miller) revisits his childhood home, where he lived with his parents Nora (Maribel Verdu) and Henry (Ron Livingston), before Henry's wrongful imprisonment for Nora's murder. Barry is a police forensic investigator from Central City. Barry requires a carbohydrates rich diet to maintain his energy levels. Iris West (Kiersey Clemons) is a journalist for the Picture News, and during a press briefing she notices Barry discreetly disagreeing with his supervisor claim that the forensic evidence in a case was sufficient. Iris realizes that Barry was in her class at school and tries to befriend him for an inside scoop.

On the day of her death, Nora sent Henry to the grocery store for a can of food that she forgot to buy, leaving her alone in the kitchen where she was killed by an unidentified assailant. Barry was in his room upstairs and when he came down, he saw Nora stabbed in the abdomen, and Henry trying to help her (in the process, getting his fingerprints over the assault knife). Henry asked Barry to rush to the neighbors and call 911. The security footage from the grocery store had Henry look down at the shelves (where the tomato can was) and not into the camera, so it could not be proven that Henry was at the store.

Overcome by emotions, Barry accidentally uses the Speed Force to form a "Chronobowl" and travels back in time to earlier that fateful day when he was rescuing babies from the hospital. Despite Bruce's warnings of time travel's unintended consequences, Barry places the can in Nora's cart at the store, so that his father will not have to leave the house. As he returns to the present, Barry is knocked out of the Chronobowl by an unknown speedster and arrives in an alternative 2013 where Nora is alive. He encounters his parents and his past self and realizes this is the day (September 29th, 2013, when Barry was 18 years old) he originally obtained his powers. The original Barry was doing an Internship at the Gotham City Crime Lab when he got his powers after an accident.

To ensure his past self gains superpowers, the two Barrys go to the Central City Police Department, where Barry re-enacts the event for 2013-Barry to be struck by lightning. Both end up getting struck by the lightning, giving 2013-Barry powers, but causing the original Barry to lose his own. As Barry struggles to train 2013-Barry on properly using his powers, they learn that General Zod (Michael Shannon) is preparing to invade Earth. General Zod is a Kryptonian general who possesses the same powers as Superman and was killed by him in an alternate Universe.

To fight Zod, the Barrys attempt to assemble the Justice League but are unsuccessful; in this time-line, Diana cannot be located, Cyborg / Victor Stone (Ray Fisher) has not gained his abilities yet, and Arthur Curry (Jason Momoa) never existed. Original Barry realizes that he created a world with no Meta-Humans. In this world Marty McFly (from Back To The Future) was played by Eric Stolz and not Michael J Fox. Tom Cruise was not Top Gun. Original Barry realizes that he broke the Universe. He learns that Batman did exist in this world.

They travel to Wayne Manor, hoping to find Bruce, but instead, they find an alternate version (Michael Keaton) who has long retired. Bruce theorizes that using time travel to alter history affects events both before and after the alteration. He says that time travel doesn't create a branch, but a fulcrum, a whole new strand of time with a different past and future. And if time travel is undertaken enough times, it leads to a multiverse. They convince Bruce to return as Batman and help them find Kal-El / Superman (Henry Cavill). Bruce says that he retired as Gotham is now one of the safest cities in the world.

2013-Bruce decides to help Barry after contemplating the situation and shares Russian intelligence reports about an alien in Siberia. 2013-Bruce then shares his plane with the Barrys to transport them to Russia. The Barrys and 2013-Batman locate a Kryptonian pod discovered in Siberia. Upon arrival, they instead find Kal-El's cousin, Kara Zor-El (Sasha Calle), imprisoned in the facility. During the escape 2013-Barry is shot in the leg, but 2013-Batman protects them and helps them escape from the facility. Kara was severely weakened due to being kept in isolation for several decades. As soon as she is exposed to the sun, she regains her powers and easily defeats the formidable prison security.

They rescue Kara and return to Wayne Manor. Kara refuses to fight Zod to save humans as humans had imprisoned her and ill-treated her for decades. Kara goes to Zod's ship that had landed on Earth, to take possession of her. She sees that humans refuse to hand her over and Zod kills all of them, prompting her to rethink her assessment of humans.

The original Barry enlists Bruce's help to regain his powers once more. The first two attempts fail, prompting Kara to fly Barry into a storm, where he regains his powers. Kara says that Barrys came to rescue Kal, but still helped her as she needed help.

Kara and Batman join the Barrys to fight Zod and his forces. During the battle, Kara learns that Zod had intercepted Kal-El's escape pod from Krypton and killed him while attempting to extract the Codex needed to repopulate the Kryptonian species. Zod reveals that the Codex is actually within Kara. Zod subdues and kills her, then extracts the Codex from her blood. Meanwhile, Batman sacrifices himself in an unsuccessful attempt to destroy Zod's ship.

The Barrys repeatedly time travel to save Batman and Kara but keep failing. Barry realizes that this sequence of events cannot be changed, but 2013-Barry keeps trying. As 2013-Barry travels, the multiverse starts to implode. Original Barry tries explaining to 2013-Barry that not every problem has a solution. The unknown speedster who initially knocked Barry out of the Speed Force returns and is revealed to be an older, future version of 2013-Barry who still believes he can defeat Zod and save his Earth. He becomes angry when original Barry reveals his intention to reverse the changes he made to the time-line by letting Nora die.

The elder 2013-Barry attempts to kill original Barry, but instead impales young 2013-Barry, who sacrifices himself to save Barry and wipe his future self from the time-line. Original Barry reverts the time-line and comes to terms with his mother's death. However, he subtly alters the past by moving the tomato cans to a higher shelf. Returning to the present day, Barry attends Henry's court hearing, where the security footage now reveals Henry looking up to grab the tomato can, allowing for his exoneration. Barry is then contacted by Bruce (George Clooney), whose appearance has changed once again as a result of the time-line alteration.