When a powerful alien threat arrives on Earth under mysterious circumstances, Barry, Iris and the rest of Team Flash are pushed to their limits in a desperate battle to save the world. But with time running out and the fate of humanity at stake, Flash and his companions will also need to enlist the help of some old friends if the forces of good are to prevail.

Barry meets Black Lightning at the Hall of Justice after things take a dire turn with Despero. Iris suspects something is off with Despero's vision of the future so she seeks help from a powerful ally.

Barry is shocked when Eobard Thawne returns in the most unexpected way, and with a tie to a loved one. Damien Darhk offers advice to Barry but there is a catch. An epic battle begins with Reverse Flash pitted against The Flash, Team Flash, Batwoman, Sentinel and Ryan Choi.

Barry's desire to keep Team Flash safe is tested when Frost recklessly courts danger as she tries to stop the "Black Flame," meanwhile, Iris tries to help a teen girl reunite with her mother but unintentionally does more harm than good.

When a criminal invades the CCPD, Barry and Kramer must trust and rely on each other if they are going to make it out safely. Meanwhile, Caitlin learns a valuable lesson while out with Snow and Mark.

Barry and Chester may have found a way to stop the "Black Flame" from hurting anyone else meanwhile Caitlin decides to handle a situation on her own, possibly putting more innocent lives in danger.

Team Flash is under attack, and each must fight to save not only themselves but each other.

Despero warns The Flash that great tragedies will befall the speedster and cause him to lose his mind. Once that happens, Armageddon will begin. Determined to prove Despero wrong, Barry doubles down on proving his innocence but a devastating revelation from Iris pushes him to the edge and sends him to seek counsel from Black Lightning.

The Flash gets blasted with a shockwave forcing his body to age prematurely.

Barry trusts his instincts during a murder investigation, believing the suspect, despite the overwhelming evidence against him, meanwhile Iris gives Allegra an opportunity to be a mentor.

The Flash and team are in for the fight of their lives, meanwhile, Iris discovers the cause of her time sickness.

An opportunity presents itself for The Flash to end his lifelong battle with Reverse Flash for good, but the payoff could be too much for Barry and team to handle. Meanwhile, Mia Queen drops in from the future looking to save a lost loved one, and she won't let anything stand in her way.

With a new Meta terrorizing the city, Joe lends a hand to the local authorities, meanwhile Barry gets an assist from Cecille who helps to track the mass murderer.

The Flash gets an assist from XS. Meanwhile, CCPD enlists Chester for help when a mysterious device is found at a crime scene.

With a new speedster in town, The Flash gets much more than he bargained for, meanwhile Cecile's powers experience a growth spurt allowing her to aid Team Flash on an entirely different level.

Team Flash uses the distraction of a bank robbing Meta to detract from the grief of losing someone they love.

With The Flash still reeling from everything that just happened, the rest of the team rallies to support him when he needs it the most.

Barry and Team Flash get closer to figuring out the Fire Meta but no closer to finding him meanwhile Iris, needing a distraction, follows a story to Coast City.

The Flash goes off the grid to look for answers about a new Meta in town. Meanwhile, Allegra pulls out all of the stops at CC Citizen Media, to protect a source and a friend.

After returning home from a visit for their parent's vow renewal, Bart and Nora quickly realize that things are not exactly as they left them. The duo race to repair any fissures in the timeline and restore everything back to the way it is supposed to be.