The adventures of scientist Barry Allen who is a superhero with incredible speed.
Cast: Grant Gustin, Candice Patton, Rick Cosnett, Danielle Panabaker, Carlos Valdes, Tom Cavanagh, Jesse L. Martin, Patrick Sabongui
After Zoom reveals his true plan, Barry vows to do whatever it takes to stop him.
Zoom unleashes an army of Earth-2 meta-humans, the leader of which is Black Canary's doppelganger, Black Siren; Joe worries when Wally goes out to help The Flash.
With Barry gone, the team must figure out a way to handle the return of Girder, an old enemy. Realizing Girder is retracing his steps from his last attack, Iris volunteers to act as bait to trap him in S.T.A.R. Labs. Meanwhile, Barry fights to return to his old life.
Zoom arrives back on Earth-1 intent on taking over Central City. Barry and Wells plan to stop Zoom but it's extremely dangerous. Unsure if he should take the risk, Barry reaches out to both fathers for advice. Meanwhile, Cisco is shocked when he senses the Earth-2 villain Rupture, who is his brother Dante's doppelgänger; and Iris decides to open up to Barry about her feelings for him.
Griffin Grey, a meta-human with super strength, mistakes Harry for Earth-1 Harrison Wells, kidnaps him and demands that Wells cure him from his current condition. Realizing another brilliant Wells could help track Griffin's location, Barry asks Jesse to help. Meanwhile, Wally corners Joe about The Flash.
Equipped with the tachyon device, Barry believes he is fast enough to stop Zoom and wants to open the breaches to catch him. Harry strongly advises against that plan but after Barry convinces him, Harry reveals that Cisco has the power to re-open the breach. Meanwhile, Hunter Zoloman's painful story on Earth-2 is revealed.
Barry becomes determined to get back to Earth-2 to stop Zoom, but he realizes he needs to increase his speed. He travels back in time and masquerades as his earlier self to get his arch-nemesis Dr. Harrison to teach him how to run faster. But while there, Barry faces familiar foe Hartley Rathaway and old friend Eddie Thawne.
Trajectory arrives in town intent on creating maximum chaos. Trajectory's antics are misinterpreted as having been perpetrated by The Flash himself. Barry must thus act quickly to uncover the mystery of who is causing damage in which others think it is him, and what may be driving their mad desire for speed and destruction.
When King Shark escapes from an A.R.G.U.S. holding tank, Lila and Diggle travel to Central City to warn The Flash. King Shark shows up at the West house and attacks Joe, Iris, Wally and Barry.
On Earth-2, the team races to find Zoom's lair and asks for help from the most unexpected source. Meanwhile, back on Earth-1, Caitlin rushes to perfect Velocity-9 so that Jay can stop the Geomancer.
Barry, Wells and Cisco journey to Earth-2 to rescue Wells' daughter, Jesse from Zoom. Barry is stunned when he runs into Earth-2 Iris and Joe, but nothing prepares him for meeting Killer Frost and Deathstorm.
Barry teams up with Wells to figure out a way to close the breaches, but they are distracted by a meta-human nicknamed Tar Pit who can transform into liquid asphalt. Iris is concerned for Wally's safety after she finds out about his drag racing hobby.
When Cisco gets a vibe of Eobard Thawne, Barry and the team don't believe it. But, after an attack at Mercury Labs, Christina McGee confirms that the Reverse Flash is back. Meanwhile, Iris and Francine share a nice moment that brings Iris closer to her brother, Wally.
Barry and the Star Labs team hunt down The Turtle who can slow down time especially anyone with speed. Barry faces a choice to whatever or not Patty should learn his secret identity especially after Zoom returns to Earth 1 to kidnap her.
Weather Wizard returns to break Captain Cold and The Trickster out of Iron Heights, but Barry is determined to not let that happen. Meanwhile, Joe and Iris meet Wally West.
When Vandal Savage attacks Kendra Saunders, Barry takes Kendra to Star City, seeking Oliver's protection; Harrison asks Jay to test a new serum to make Barry run faster.
Barry races to rescue Caitlyn when Grodd kidnaps her; Cisco plans a date with the new barista at Jitters; Patty thinks Barry is hiding something.
Barry, Caitlin, Cisco, Iris, Joe, and Dr. Wells formulate a plan to lure Zoom Earth 2 to their world by getting Linda to pose as Dr. Light and trap Zoom.
Barry learns a new breacher, Dr. Light, has come through the portal and sets off to capture her. Jay tells Barry that Dr. Light was not a threat on Earth-2 and that Barry can reason with her. However, during a fight with The Flash, she blinds him and drops some shocking news about Zoom. Meanwhile, Barry and Patty go out on a date.
Barry and the team look for another Firestorm match for Dr. Stein. When the team meets Jefferson Jackson, Caitlin has her reservations about whether Jax is the right match for Dr. Stein. Iris surprises Joe while Barry and Patty grow closer.
Barry and the team ally with the kidnapped Captain Cold's sister, but Barry feels duped with he learns Snart is working on something with his father; Joe faces a difficult decision.
A mysterious man has a warning about an evil speedster intent on destroying The Flash; a determined officer wants to join Joe's meta-human task force.
Still feeling responsible for Eddie's death, Barry pushes his friends away and tries to protect the city on his own; Cisco assists Joe with the Meta Task Force.