PILOT
Forensic scientist Barry Allen is struck by lightning and doused in chemical products that afford him superhuman speed, which he learns to control with help from Tina McGee, a scientist from S.T.A.R. Labs. When Barry's brother, policeman Jay Allen, is murdered by his corrupt ex-partner, Nicholas Pike, the leader of a vicious motorcycle gang of criminals, Barry uses his newfound abilities to bring Pike and his gang to justice and decides to continue protecting Central City as "The Flash".
OUT OF CONTROL
While Barry and his colleague Julio Mendez investigate the murders of several homeless people whose bodies are being stolen from the crime scenes, Tina reconnects with an old friend, Dr. Carl Tanner, who has recently returned to Central City to retrieve Tina's late husband's research on genetic engineering. Barry and Tina learn that Tanner is using the vagrants in his lethal illegal experiments to create mutations, and upon being confronted, Tanner injects himself with the unfinished serum, turning into a man monster that only the Flash manages to defeat.
WATCHING THE DETECTIVES
Barry's secret identity is uncovered by Megan Lockhart, a private investigator employed by corrupt District Attorney Thomas Castillo, whose collaborator, mobster Arthur Simonson, has hired an arsonist to torch buildings in the waterfront area as part of Castillo's efforts to bring legalized gambling into Central City on behalf of the organized crime. Castillo blackmails Barry into becoming his secret accomplice, enabling Barry to acquire evidence of Castillo's crimes, including his plans to control the mob bosses and seize control of their business. Upon learning of this, Simonson rigs a bomb in Castillo's car and Castillo is subsequently assassinated when he turns the ignition. Lockhart, having grown attracted to Barry, surrenders the evidence to Barry she had compiled in order to protect his secret.
HONOR AMONG THIEVES
Master thief Stan Kovacs assembles a team of professional thieves, who the police believe intend to steal the Mask of Rasputin from the museum of natural history. While they are distracted guarding it, Kovacs masterminds a string of robberies across Central City, which are foiled by the Flash, and in the process Barry learns that Kovacs is using the other criminals as a diversion so his accomplice Celia Wayne can steal the relic from the museum's curator and Barry's mentor, Ted Preminger. The Flash catches up to Kovacs and Celia before they escape with the artifact and brings them to justice, insuring that Preminger can finance the museum with the Rasputin Mask exhibit.
DOUBLE VISION
Barry attempts to foil the kidnapping of Paloma Aguilar, daughter of DEA agent Peter Paul Aguilar, who is scheduled to testify against drug lord Reuben Calderon. However, Calderon's enforcer, Marcos Trachman, utilizes a potentially fatal advanced microscopic device to control Barry's nervous system and force him to help them kidnap Paloma before Tina manages to jam the devices' signal. Barry and Tina then race against time to prevent a brainwashed Paloma from murdering her father while under Trachman's control, and once he's defeated, he agrees to testify against Calderon, leading to Calderon's conviction. Trachman suffers a "short circuit" after a fight with The Flash.
SINS OF THE FATHER
Barry attempts to protect his father, veteran policeman Henry Allen, from Johnny Ray Hix, a dangerous criminal that Henry arrested 15 years prior and who has escaped from prison to enact revenge. Henry is initially dismissive of Barry's attempts to use forensic science, which Henry rejects, to locate Hix, but they prove vital when Hix murders Henry's old partner Pete Donello and hires a hitman who nearly kills Henry. The Flash rescues him and brings Hix to justice, while Barry and Henry finally make amends.
CHILD'S PLAY
Barry shelters street orphans Terry and Cory Cohan, who have stolen the knapsack of a recently murdered journalist, Philip Sullivan, containing Sullivan's research on a highly addictive synthetic drug known as "Blue Paradise" on a floppy disk, developed by notorious drug designer Beauregarde Lesko. Terry is nearly turned into an addict while meeting Lesko to exchange the disk for $1 million dollars, and Barry subsequently defeats Lesko and dismantles his operation before Blue Paradise can be unleashed in Central City, while Terry and Cory are adopted by Sullivan's widow, Joan.
SHROUD OF DEATH
Lieutenant Warren Garfield stonewalls Barry and Julio's efforts to locate a cloaked figure who is targeting individuals connected to the arrest and conviction of notorious anarchist Jefferson Zacharias, who was executed after having been given the death penalty. Barry realizes Garfield was the arresting officer just as Garfield's fianc e, Mavis, is critically injured by the killer, revealed to be Zacharias' daughter, Angel, who then lures Garfield into a trap. The Flash intervenes, saves Garfield's fianc e and then prevents Garfield from killing her in revenge. Garfield then marries Mavis.
GHOST IN THE MACHINE
In 1955, Central City's guardian was Desmond Powell, who fought crime as "The Nightshade". His last nemesis, a criminal mastermind known as "The Ghost", is believed to have died after a confrontation, causing a guilt-stricken Powell to retire. However, the Ghost has in fact preserved himself in cryogenic suspended animation and resurfaces in 1990, where he hijacks Central City's power grids and holds the city for ransom, forcing Powell to return to action and join forces with the Flash. Together, they defeat the Ghost, who had wired himself into the city's electrical network, and save the city.
SIGHT UNSEEN
Brian Gideon, a disturbed chemical engineer, learns that S.T.A.R. Labs is producing nerve toxins based on his research for the United States government and uses a stealth device to infiltrate S.T.A.R. Labs and retrieve the toxins. His plan traps Tina and her employer Ruth Wenerke in the lab, where they are exposed to a deadly neurotoxin. While attempting to locate both Gideon and a cure, Barry clashes with federal agent Jack Quinn, who is trying to cover up his own involvement in the emergency. Barry confronts Gideon, who injects him with the toxin in order to escape, but Barry is able to burn it out of his body, and use his blood to inoculate Tina and Ruth. Gideon is then arrested, while Ruth cuts ties with Quinn, who is suspended when the activities he illegally sanctioned for Gideon are exposed.
BEAT THE CLOCK
Barry and Julio are tipped off that Wayne Cotrell, a famous Jazz saxophonist on the death row for the murder of his wife, lounge singer Linda Lake, is innocent, and they have less than an hour to find evidence to acquit him. They ultimately learn that Linda was kidnapped by Wayne's brother, Elliott Cotrell, who wanted to ruin his brother's life out of jealousy, and that his enforcer, an ex-warlord and singer nicknamed "Whisper", murdered another woman, who was then put in Linda's place in a fixed car accident designed to lead back to Wayne. After incapacitating Whisper, Barry carries Linda to the execution chamber. They arrive in the nick of time to save Wayne before the execution is carried out. Wayne is reunited with Linda, while Elliott is arrested.
THE TRICKSTER
James Jesse, a serial killer with multiple personalities, becomes obsessed with Megan Lockhart, who had been investigating his activities, and attempts to kidnap her, but she is rescued by the Flash. Believing them to be romantically involved, Jesse adopts the identity of the Trickster and begins tormenting the Flash and terrorizing the city. The Flash ultimately lures Jesse into a fight at the police's costume ball, where he is finally caught and arrested. Despite Barry and Megan becoming previously involved, she decides to leave Central City and ends their relationship.
TINA, IS THAT YOU?
Barry becomes plagued with nightmares and cannot sleep normally due to his double life as The Flash. In an attempt to help Barry sleep again, a bio-feedback experiment gone awry causes Tina to develop a malevolent personality, and after the accidental death of the leader of an all-female gang, called the Black Rose, she seizes control of the gang. When Barry foils their latest robbery, Tina decides to lure Barry into a trap and kill him and a blind date he was with, but Barry manages to escape, prevent Tina from leaving town with the gang and leaving the Black Rose and a tattoo parlor owner known as "Big Ed", who was hiding them, for the police. Barry takes Tina back to S.T.A.R. Labs, and using the bio-feedback device to restores her to normal.
BE MY BABY
Barry crosses paths with Stacy Doubek, the daughter of Nobel prize winning academics, and her young daughter, Lily, who are fleeing Lily's father, mobster Philip Moses (Bryan Cranston), who wants the child as his heir. After the Flash prevents Moses from kidnapping Lily, Garfield attempts to use her in a sting operation to lure Moses into a trap, but Moses is tipped off by a man in the police force and manages to escape with Lily. The Flash chases him to an abandoned airfield and prevents him from leaving Central City, and Moses is arrested while Stacy and Lily are reunited and decide to stay in Central City.
FAST FORWARD
Nicholas Pike is released from prison on a technicality and attempts to use a missile to kill the Flash, instead transporting him 10 years into the future to the year 2001, where Barry's secret identity has been exposed and Pike has conquered the now dystopian city. Aided by his old friends, Barry regains his speed and manages to return to the past, capturing Pike once again and saving the city.
DEADLY NIGHTSHADE
Philanthropist Curtis Bohannan, son of Derek Bohannan, a mobster fought by the Nightshade in the 1950s, becomes a copycat vigilante known as "The Deadly Nightshade", who employs lethal force in his crusade against crime. Garfield is sent evidence that Powell, an old friend of his, is the Nightshade and arrests him, only for Powell to be kidnapped by Bohannan, who wants Powell to join him. Barry locates them and Powell saves Barry from Bohannan who is armed with an accelerated Exo-Skeleton suit. Powell then decides to reveal his secret identity to the world.
CAPTAIN COLD
Mobster Jimmy Swain employs hitman Leonard Wynters, also known as "Captain Cold" for his weapon of choice, a nuclear-powered freeze ray, to eliminate his competitors and then the Flash. Barry's investigation is hampered by Terri Kronenberg, a tabloid reporter for the National Inquisitor. After killing Swain for firing him after his failure to kill The Flash in the first attempt, Wynters nearly kills Barry after Kronenberg gets in the middle of them during a confrontation. Wynters is caught by The Flash after he attempts to kill her in her apartment. Wynters later escapes prison and lures the Flash into a trap, hellbent on completing his contract out of honor, but Barry outsmarts him due to a device that preserves his body heat, and diverts Wynters' beam against him, encasing Wynters in ice.
TWIN STREAKS
Barry is cloned by Dr. Jason Brassel, who names the clone "Pollux", who Brassel designs a blue variant suit for. Upon learning that he is a clone and not a real person, Pollux goes on a rampage and comes into conflict with the Flash, who is currently suffering symptoms of stress and fatigue. Brassel attempts to kill Barry after Pollux throws a bullet into him, but Pollux takes the bullet and dies in Barry's arms, while Brassel succumbs from the injuries Pollux had earlier inflicted on him.
DONE WITH MIRRORS
Sam Scudder, a criminal mastermind who uses mirrors and holograms to commit his crimes, steals an advanced battery from S.T.A.R Labs Silicon Valley division, which is then stolen from him by his partner, Anastasia Masters, who flees to Central City and seduces her former classmate Barry into sheltering her at his apartment. Scudder kidnaps both Barry and Tina's mother Jocelyn Weller, whom he mistakes for Stasia's buyer, to force Stasia to deliver the battery, and Barry ultimately realizes Stasia is manipulating him. He rescues Tina, who had been lured to the station where Stasia was trying to sell the battery, pummels Scudder and arrests Stasia, returning the battery to S.T.A.R Labs.
GOOD NIGHT, CENTRAL CITY
Petty crook Harry Milgrim and his cousin, scientist Roger Braintree, plan to use a soundwave device developed by Braintree, which places people in an induced slumber, to rob Central City. Milgrim fakes his death during a test run, then pins the blame for a robbery on Barry, who races against time to both prove his innocence and prevent Milgrim, Braintree and a group of professional gangsters from conducting a citywide robbery after discovering the induced sleep is fatal if the sleepers sleep too long. In the end, Barry triumphs, with Milgrim, who had killed Braintree, is arrested, clearing his name, and humiliating an over eager internal affairs agent.
ALPHA
Barry and Tina befriend Alpha, an android assassin developed by the NSIA a United States government division who refuses to kill, and protect her from another android assassin, Omega, send to retrieve her. The Flash ultimately destroys Omega and helps Alpha evade the NSIA and escape Central City before a bomb inside her goes off. Later she leaves to start her life anew.
THE TRIAL OF THE TRICKSTER
James Jesse is brought to trial for his previous rampage in Central City. Jesse later escapes from the courtroom with help from an obsessive fan, Zoey Clark, and becomes the Trickster once again, with Clark as his assistant, Prank. They brainwash the Flash into joining them in wreaking havoc, damaging the Flash's public image, but Jesse ultimately betrays Clark and leaves her to the police. Tina and Megan join forces and manage to break Barry free in time to prevent Jesse from executing the lawyers and the Judge involved in his trial. Jesse is then captured and put into a padded cell, while the Flash is embraced as a hero by the people of Central City. Barry turns down an offer to move to San Francisco with Megan because he is not ready to say goodbye to Central City.