Season synopsis
Contains spoilers for this season and earlier seasons.
When a particle accelerator explosion leaves Central City forensic scientist Barry Allen in a nine-month coma, he wakes with extraordinary speed. He teams up with S.T.A.R. Labs scientists Caitlin Snow and Cisco Ramon, along with detective Joe West, to stop people whose abilities were changed by the blast. Barry uses the name the Flash as he protects the city, while Joe and Iris West's boyfriend, detective Eddie Thawne, investigate the mysterious speedster connected to Barry's mother's murder.
Caitlin's supposedly dead fiancé Ronnie Raymond returns as Firestorm after the explosion fused him with physicist Martin Stein. Meanwhile, Barry's mentor Harrison Wells is secretly Eobard Thawne, a speedster from the future who killed Barry's mother and has been steering Barry's development so he can return to his own time. Eobard's identity comes to light after Barry travels back a day during a failed attempt to stop a tidal wave, and the team discovers that Wells has been watching and manipulating them for years.
Eobard kidnaps Eddie, revealing that Eddie is his distant ancestor, and uses the repaired accelerator to open a route home. Barry enters the past but, warned by a future version of himself, does not prevent his mother's murder; he returns and destroys Eobard's time machine. As Eobard gains the upper hand, Eddie shoots himself to end the family line that would produce the villain, and Eobard vanishes. The accelerator's wormhole then becomes a destructive singularity, and Barry races into the expanding breach as the season ends.