When Barry Allen wakes up in S.T.A.R. Labs, he learns that the explosion of a particle accelerator made him into a metahuman, a person with extraordinary abilities. Dr. Harrison Wells encourages him to use his speed to combat the evil machinations of other metahumans.
As Barry's speed starts to take its toll on his body, the team at S.T.A.R. Labs steps in to help. Joe and Barry team up to look into the murder of Barry's mother.
Barry and Joe investigate a murder that was committed by a metahuman. The team's attempt to create a prison to contain the criminal metahumans stirs up painful memories for Caitlin.
Iris and Eddie deal with Joe's disapproval of their relationship. The newest villain in town gets his hand on a weapon designed by Cisco that may spell the end to the Flash.
Barry tries to help a struggling metahuman with a military general on her tail, but his attempt backfires, leaving the entire city in danger.
A face from Barry's past returns to haunt him, putting Iris's life in danger. Joe gets an unwelcome guest as a result of his investigation of Nora Allen's murder. On Barry's advice, Iris starts to refer to Central City's newest hero as the Flash.
When an attack from a meta drains Barry of his speed, the future threatens to change, much to Wells' frustration. Eddie's life hangs in the balance in the wake of a hostage situation at the police station.
In pursuit of a criminal, Oliver Queen arrives in Central City, but an attack from a meta pits the Flash and the Green Arrow against each other.
Nora Allen's murderer makes a return, raising more questions for Barry as he comes face-to-face with the man who destroyed his life. A new meta turns out to be someone familiar to the team at S.T.A.R. Labs.
Leonard Snart returns to lay a trap for the Flash, landing one of his friends in danger as Snart seeks to lure the Flash into a confrontation.
The Flash is up against a new threat as Wells' former protégé, Hartley Rathaway, uses his intelligence against the team, taunting them with his knowledge of Ronnie's location.
After a break into Iron Heights, Henry tries to find leads for Barry to pursue. The team gets new information about what happened to Ronnie.
The team pulls out all the stops to save Ronni and Stein after they make a discovery about their abilities. Cisco makes a discovery in the investigation into Nora's murder.
As the military goes after Ronnie and Stein, the two learn more information about their fusion and their abilities. Wells makes a move to eliminate danger to Barry. Iris grows suspicious of the S.T.A.R. Labs team.
A vengeful meta threatens the lives of the people Barry care most about. Cisco makes a discovery about Wells and his real plans for Barry.
Cisco is forced to help Snart and his companions after a threat to his brother. Barry's attempt to manipulate the timeline creates tension with Eddie and Iris.
The imprisoned Trickster gets broken out of prison by a copycat, and the two wreak havoc upon Central City. Barry confides in Eddie and Joe as he prepares to take on Wells.
As killer bees take over Central City, Barry receives help from some familiar faces. In the face of shocking news from Barry, Cisco reveals that he has been seeing visions from an alternate timeline.
In a search for information on Wells, Cisco and Joe head to Starling city and uncover a shocking secret. Barry races to save Eddie after a meta frames him for murder.
As the team uncovers the whole truth about Wells, Barry comes up with a plan to entrap him, but the plan backfires, leaving one of them in danger.
Barry enlists the help of Snart to rescue the imprisoned metahumans as Thawne's plan to charge the particle accelerator puts their survival in question.
As the psychic gorilla Grodd launches an attack, the team is forced to balance dealing with the attack with searching for Eddie and Thawne.
Barry is forced to relive the night of his mother's murder as Thawne makes him a tempting offer. Eddie steps in to help when Thawne gets the upper hand over Barry.