Months after having saved the city Barry Allen has isolated himself from his friends, holding a silent guilt over the prices paid. But when a meta-human assassin targets the Flash, his friends rally to help him. Meanwhile, Barry receives a life-changing message from Harrison Wells.

After a man claiming to be from a parallel world approaches the team with a dire warning about an evil speedster named Zoom, Barry must decide whether Jay Garrick can be trusted. Meanwhile an Earth-2 meta-human, nicknamed "Sand Demon," targets the Flash -- and his newest friend, CCPD officer Patty Spivot, who is petitioning to join Joe's meta-human task force.

After Captain Cold's sister tells the team that he has been kidnapped, Barry discovers that their ruthless father is forcing Leonard to help him pull off a heist. Meanwhile Joe wrestles with telling Iris the truth about her mother, and Jay asks for Caitlin's help in stabilizing the dimensional breach inside S.T.A.R. Labs.

With Dr. Stein running out of time Barry, Caitlin, and Cisco search for a new match for the Firestorm matrix -- leading them to a washed-up football player named Jefferson Jackson. Meanwhile, Iris confronts her mother only to receive a starting revelation about her.

The team tries to adjust to the arrival of Dr. Wells' doppelganger from Earth-2, who has a tense relationship with Jay but crucial knowledge of Zoom. Meanwhile Barry squares off against a meta-human known as Dr. Light, only to learn that she is the double of someone he knows.

With help from Dr. Light, Barry plans to lure Zoom into a trap to confront the evil speedster face-to-face -- despite the misgivings of those close to him. Cisco tries to use his abilities to discover Wells' secret agenda.

When Grodd returns to Central City and kidnaps Caitlin, the team must find a way to rescue her without Barry's speed. Meanwhile Henry Allen returns to town to help his son recuperate from his recent injuries, and Cisco gets a surprise on his date with Kendra Saunders.

Barry and his friends travel to Star City for help protecting Kendra Saunders from an immortal assassin named Vandal Savage, only to learn that she must rediscover her own secret past. Meanwhile, Wells tries to convince Jay Garrick to test a drug that might boost the Flash's speed.

Weather Wizard breaks Captain Cold and the Trickster out of Iron Heights on a mission to trap and kill the Flash at Christmastime. Meanwhile Wells debates an offer from Zoom, and Iris decides to tell her father that he has a son.

Barry resolves to tell Patty that he is the Flash, while the team hunts for a meta-human nicknamed "the Turtle" -- whose ability to slow down time might help them stop Zoom. Meanwhile, Joe finds it difficult to make a connection with Wally.

When Cisco discovers that Eobard Thawne has inadvertently returned to their time, Barry sets out to stop his nemesis once and for all. Iris must reconcile with her mother as Francine's health worsens, and Patty confronts Barry before she leaves town.

While a meta-human who can transform into liquid asphalt targets the men who tried to kill him, Barry remains unaware that someone close to him is stealing his speed. Meanwhile Iris puts herself in harm's way to try and get Wally to stop drag racing.

Barry, Cisco, and Wells travel to Earth-2 with a plan to track Zoom and rescue Wells' daughter, Jesse -- only to encounter super-powered villains Killer Frost and Deathstorm. Back on Earth-1, Jay Garrick may be the only one who can stop a meta-human who can generate earthquakes.

Cisco and Wells must convince Killer Frost to lead them to Zoom's lair on Earth-2 in the hopes of rescuing Barry, who finds himself imprisoned with Jesse and a masked stranger. Back on Earth-1, Caitlyn tries to perfect the Velocity formula so that Jay can stop the Geomancer.

Lila and Diggle arrive in Central City with a warning after King Shark escapes from an A.R.G.U.S. holding tank, setting his sights on taking out the Flash. Meanwhile Cisco worries that Caitlin's grief could drive her closer to her evil, Earth-2 counterpart, and Barry finds it difficult to bond with a resentful Wally.

After Central City falls victim to a new speedster who is using her powers to steal, Barry discovers that even he can't keep up with her. The team's investigation leads to Caitlin's Velocity 9 formula, and Cisco vibes some important new intel about Zoom. Meanwhile, Iris's relationship with her new boss strikes a personal note after he orders her to write a story against the Flash.

Determined to learn how to go fast enough to stop Zoom, Barry decides to travel back one year into the past and pose as his younger self to gain intel from none other than Eobard Thawne. But when a ghoulish Time Wraith follows him back, Barry must improvise to stop the creature and avoid changing the timeline.

Convinced he has acquired enough speed to beat Zoom, Barry looks to open a breach -- making a way for his enemy to come through and once again wreak havoc on the people he loves. Harry reveals Hunter Zoloman's frightening history on Earth-2.

Barry struggles with life without his speed, which is further complicated when Harry is kidnapped by a super-strong meta who blames him for the particle accelerator explosion. On Earth-2, Caitlyn finds herself face-to-face with her evil doppelganger.

Zoom returns to Earth-1 and announces his intention to take control of Central City, and Barry must decide whether to wager his life in a risky plan to restore his speed. Cisco reconnects with his estranged brother after vibing him -- only to learn that his Earth-2 doppelganger is hunting them.

Following Barry's disappearance the team tries desperately to rescue him from another realm, where a series of familiar faces force him to confront some unresolved business. Meanwhile Iris must act as bait to catch Girder after the meta-human's corpse is reanimated.

Zoom unleashes an army of Earth-2 meta-humans on Central City -- including an evil version of Laurel Lance. Meanwhile Wally puts himself at risk to try and help the Flash, Barry's loved-ones become concerned about his confidence level following his recent experience, and Cisco has a vision of the end of the world.

Zoom challenges the Flash to a race, revealing his plan to destroy the multiverse. But when an emotional Barry threatens to put everyone at risk, his friends take drastic measures to try and stop the evil speedster on their own.