In the wake of Nora's death, Barry and Iris have trouble moving on until a new threat presents itself, forcing the couple to rely on Nora's tech to save the city. Caitlin's colleague Ramsey tries a risky gambit to develop a cure for incurable diseases.
Barry's attempt to find out more about the upcoming Crisis leaves him despondent. Cecile makes a decision about her career after getting involved in the case of a young metahuman called Allegra.
Ramsey's experiment backfires, leaving the city to face the threat of a zombified gunrunner. Barry tries to prepare Killer Frost for the aftermath of his death. Ramsey makes a discovery that might enable his search for a cure for his illness.
As Cisco becomes consumed with the thought of saving Barry, Nash Wells offers his help. Despite Barry's attempt to save Ramsey, he continues to devolve and fully succumbs to his darkest desires.
As the news of Cynthia's murder reaches Cisco, his search for the culprit puts his own life on the line. Joe grows suspicious of Nash, leading to a confrontation where Nash reveals his secret pursuit of the Monitor.
Barry teams up with Ralph on one of his investigations in an attempt to prepare him for life after Crisis. Nash enlists Allegra's help as he continues to look for eternium, assuring her that using her powers won't turn her into her cousin.
While trying to save Ralph, Barry ends up infected by some of Ramsey's blood, giving the latter the chance to try and lure Barry to his side. As Barry has a confrontation with the Speed Force, Barry's friends try to get him back before Ramsey gains full control of him.
As Ramsey plots to launch a full-scale attack to transform the citizens of Central City into his minions, Iris and Cisco struggle to find a way to contain him and save Barry, especially as the Crisis looms near.
With the last three Paragons identified, Iris tries to get one of the Paragons on their side. Pariah is forced to recruit Black Lightning from another Earth to help, as Barry faces the fate that the Monitor has warned him about.
As Barry tries to honor Oliver's sacrifice, Iris becomes determined to expose the secret organization Black Hole. Cisco embarks on a journey to deal with the aftermath of the Crisis.
Barry and Iris get stuck in the middle of a dispute between Amunet and Goldface. Nash starts having mysterious hallucinations of one of his doppelgangers.
As Ralph finally locates his missing client, Sue Dearbon, he discovers that the case involves more than he bargained for. Iris meets Eva McCulloch in the Mirrorverse as her double in the real world deceives Barry.
A mishap ends with Barry reuniting with Gorilla Grodd, leading to a shocking revelation. Allegra makes a discovery about Nash's past as he continues to suffer from hallucinations.
As Wally returns to voice his concerns about the Speed Force to Barry, the two are forced to confront the effects its impending destruction will have on them. Cisco confronts an old enemy in the form of a familiar face.
As Team Flash tries to help Nash, the latter's traumatic past comes to light. The Mirror doubles manipulate Barry and the rest of the team as they continue to enact Eva's mysterious plan.
As Barry struggles with what his waning speed means for his ability to protect his family and friends, Eva uses Mirror Iris to ensure that Barry loses his powers. Joe's life hangs on the line after Carver sends an assassin after him.
As Barry becomes suspicious of Mirror Iris, Eva steps in to manipulate the rest of Team Flash to ensure the success of her plans. Caitlin is forced to confront the effect of her fight with Sunshine.
As Godspeed launches an attack, Barry is forced to enlist the help of a familiar face, only to confront another change in the post-Crisis world. Iris struggles to hold onto mental faculties in the Mirrorverse.
Barry races to save Carver from Eva before it's too late. Sue gets drawn into the confrontation between Team Flash and the Black Hole assassins. Eva implements the last step in her plan.